@@ -132,7 +132,7 @@ export function SpectroscopeCalculator() {
{isValid && (
diff --git a/src/components/optical/DichroscopeResults.tsx b/src/components/optical/DichroscopeResults.tsx
index 230c892..1211d8a 100644
--- a/src/components/optical/DichroscopeResults.tsx
+++ b/src/components/optical/DichroscopeResults.tsx
@@ -22,16 +22,16 @@ const FALLBACK_DICHROIC_GEMS: DichroscopeData[] = [
{ gem: 'Ruby', color1: 'Red', color2: 'Orange-red', strength: 'Strong', notes: 'Best seen in thick stones' },
{ gem: 'Sapphire (Blue)', color1: 'Blue', color2: 'Greenish-blue', strength: 'Strong', notes: 'Varies with saturation' },
{ gem: 'Emerald', color1: 'Blue-green', color2: 'Yellow-green', strength: 'Moderate', notes: 'More visible in darker stones' },
- { gem: 'Alexandrite', color1: 'Red/Purple', color2: 'Orange/Green', color3: 'Green', strength: 'Very Strong', notes: 'Color change + pleochroism' },
- { gem: 'Tanzanite', color1: 'Blue/Violet', color2: 'Purple/Red', color3: 'Bronze', strength: 'Very Strong', notes: 'Trichroic — see 3 colors' },
+ { gem: 'Alexandrite', color1: 'Red/Purple', color2: 'Orange/Green', color3: 'Green', strength: 'Very Strong', notes: 'Colour change + pleochroism' },
+ { gem: 'Tanzanite', color1: 'Blue/Violet', color2: 'Purple/Red', color3: 'Bronze', strength: 'Very Strong', notes: 'Trichroic; shows 3 colours' },
{ gem: 'Tourmaline (Green)', color1: 'Dark green', color2: 'Light green', strength: 'Strong', notes: 'Best down c-axis' },
{ gem: 'Tourmaline (Pink)', color1: 'Dark pink', color2: 'Light pink', strength: 'Strong', notes: 'Visible in most directions' },
- { gem: 'Iolite', color1: 'Violet-blue', color2: 'Pale yellow', color3: 'Colorless', strength: 'Very Strong', notes: 'Dramatic color shift' },
- { gem: 'Andalusite', color1: 'Red-brown', color2: 'Yellow-green', color3: 'Green', strength: 'Very Strong', notes: 'Distinctive colors' },
- { gem: 'Kunzite', color1: 'Violet', color2: 'Colorless/Pink', strength: 'Strong', notes: 'Fades in light' },
+ { gem: 'Iolite', color1: 'Violet-blue', color2: 'Pale yellow', color3: 'Colourless', strength: 'Very Strong', notes: 'Striking colour shift' },
+ { gem: 'Andalusite', color1: 'Red-brown', color2: 'Yellow-green', color3: 'Green', strength: 'Very Strong', notes: 'Distinctive colours' },
+ { gem: 'Kunzite', color1: 'Violet', color2: 'Colourless/Pink', strength: 'Strong', notes: 'Fades in light' },
{ gem: 'Peridot', color1: 'Green', color2: 'Yellow-green', strength: 'Weak', notes: 'Subtle difference' },
- { gem: 'Aquamarine', color1: 'Blue', color2: 'Colorless/Pale blue', strength: 'Weak', notes: 'Often not visible' },
- { gem: 'Topaz (Blue)', color1: 'Colorless', color2: 'Pale blue', strength: 'Weak', notes: 'Difficult to detect' },
+ { gem: 'Aquamarine', color1: 'Blue', color2: 'Colourless/Pale blue', strength: 'Weak', notes: 'Often not visible' },
+ { gem: 'Topaz (Blue)', color1: 'Colourless', color2: 'Pale blue', strength: 'Weak', notes: 'Difficult to detect' },
{ gem: 'Morganite', color1: 'Pink', color2: 'Pale pink', strength: 'Weak', notes: 'Requires good stone' },
];
@@ -116,7 +116,7 @@ export function DichroscopeResults() {
{/* Filter bar — single row across full width */}
- First Color
+ First Colour
-
Second Color
+
Second Colour
) : (
-
No matching gems found. Try different color terms.
+
No matching gems found. Try different colour terms.
)}
{/* Usage tips — inline */}
• Isotropic gems (cubic) show no pleochroism
- • Uniaxial gems show 2 colors
- • Biaxial gems can show 2–3 colors
+ • Uniaxial gems show 2 colours
+ • Biaxial gems can show 2–3 colours
• Best viewed in strong light against white
diff --git a/src/components/optical/OpticalTools.tsx b/src/components/optical/OpticalTools.tsx
index cb79e4f..1787ee4 100644
--- a/src/components/optical/OpticalTools.tsx
+++ b/src/components/optical/OpticalTools.tsx
@@ -20,7 +20,7 @@ export function OpticalTools() {
diff --git a/src/components/quiz/study/LearnQuizWidget.tsx b/src/components/quiz/study/LearnQuizWidget.tsx
index 037da85..6d15f22 100644
--- a/src/components/quiz/study/LearnQuizWidget.tsx
+++ b/src/components/quiz/study/LearnQuizWidget.tsx
@@ -168,7 +168,7 @@ export function LearnQuizWidget({
The article below covers each of these topics in depth. Pay particular
- attention to any questions you got wrong — the pretesting effect makes
+ attention to any questions you got wrong; the pretesting effect makes
the content that follows measurably stickier.
diff --git a/src/content/questions/equipment/ri-reading-001.yaml b/src/content/questions/equipment/ri-reading-001.yaml
index 6de4878..5b48372 100644
--- a/src/content/questions/equipment/ri-reading-001.yaml
+++ b/src/content/questions/equipment/ri-reading-001.yaml
@@ -6,17 +6,17 @@ stem: |
it indicate about the stone's optical character?
type: mcq
options:
- - text: "Pattern I — the stone is isotropic"
+ - text: "Pattern I: the stone is isotropic"
isCorrect: false
rationale: |
Pattern I does produce a single constant shadow edge, but the RI of 1.544 is
consistent with quartz, not an isotropic gem [ref:read-gemmology-3e]. Quartz is uniaxial positive,
not isotropic. A single constant edge can arise from Pattern I (isotropic) or
from a uniaxial stone viewed down its c-axis [ref:read-gemmology-3e]. At RI 1.544, quartz (Pattern II
- or III reading omega) is a more accurate interpretation — but this distractor
+ or III reading omega) is a more accurate interpretation; but this distractor
tests whether students conflate "one constant edge" with isotropic character
exclusively [ref:anderson-gem-testing].
- - text: "Pattern II — the stone is uniaxial with its c-axis perpendicular to the table facet"
+ - text: "Pattern II: the stone is uniaxial with its c-axis perpendicular to the table facet"
isCorrect: false
rationale: |
Pattern II shows two constant, parallel edges that remain fixed during rotation [ref:read-gemmology-3e].
@@ -24,7 +24,7 @@ options:
rules out Pattern II. A student might choose this because they know quartz is
uniaxial and assume any uniaxial reading shows two edges, but Pattern II requires
exactly two constant parallel edges to be visible simultaneously [ref:read-gemmology-3e].
- - text: "Pattern I — the stone displays one constant shadow edge, consistent with isotropic or a uniaxial stone viewed down its optic axis"
+ - text: "Pattern I: the stone displays one constant shadow edge, consistent with isotropic or a uniaxial stone viewed down its optic axis"
isCorrect: true
rationale: |
Pattern I is defined as a single shadow edge that remains constant during full
@@ -36,7 +36,7 @@ options:
without re-examining the stone on a different facet [ref:anderson-gem-testing].
rationaleCorrect: |
Pattern I is defined as one constant shadow edge throughout full rotation [ref:read-gemmology-3e]. The key
- teaching point is that Pattern I does NOT prove isotropic character — it could also
+ teaching point is that Pattern I does NOT prove isotropic character; it could also
mean a uniaxial stone is oriented with its c-axis perpendicular to the hemisphere
(i.e. you are looking down the optic axis) [ref:read-gemmology-3e]. At RI 1.544, quartz omega is the classic
match: to determine whether this is an isotropic gem or quartz viewed down c, the
diff --git a/src/content/questions/equipment/ri-reading-002.yaml b/src/content/questions/equipment/ri-reading-002.yaml
index ed48034..d1effc5 100644
--- a/src/content/questions/equipment/ri-reading-002.yaml
+++ b/src/content/questions/equipment/ri-reading-002.yaml
@@ -16,7 +16,7 @@ options:
edge) is greater than omega (the constant edge), the stone is uniaxial positive [ref:read-gemmology-3e].
Here epsilon 1.691 > omega 1.662, so the stone is uniaxial positive. Birefringence
is 1.691 − 1.662 = 0.029.
- - text: "Pattern IV; uniaxial or biaxial — optic sign indeterminate"
+ - text: "Pattern IV; uniaxial or biaxial; optic sign indeterminate"
isCorrect: false
rationale: |
Pattern IV shows one constant and one variable edge that do NOT touch during
@@ -30,8 +30,8 @@ options:
isCorrect: false
rationale: |
For uniaxial negative, the constant omega must be greater than the variable
- epsilon — that is, the constant edge must lie at a higher RI than the variable
- one [ref:read-gemmology-3e]. In this case, the constant edge is at 1.662 and the variable edge rises
+ epsilon (that is, the constant edge must lie at a higher RI than the variable
+ one) [ref:read-gemmology-3e]. In this case, the constant edge is at 1.662 and the variable edge rises
to 1.691, meaning epsilon > omega. Choosing "negative" reverses the sign rule.
The mnemonic is: positive = epsilon exceeds omega [ref:anderson-gem-testing].
rationaleCorrect: |
@@ -40,7 +40,7 @@ rationaleCorrect: |
only pattern that unambiguously confirms uniaxial character AND allows optic sign
determination from the refractometer alone. The sign rule: epsilon > omega = positive;
omega > epsilon = negative [ref:read-gemmology-3e]. Here epsilon 1.691 > omega 1.662, giving uniaxial positive.
- Note: never confuse Pattern III (edges touch) with Pattern IV (edges do not touch) —
+ Note: never confuse Pattern III (edges touch) with Pattern IV (edges do not touch);
the touch/no-touch test is the single most tested distinction in FGA refractometer
questions [ref:anderson-gem-testing].
difficulty: 3
diff --git a/src/content/questions/equipment/ri-reading-003.yaml b/src/content/questions/equipment/ri-reading-003.yaml
index 7a1f8d3..67d1cc5 100644
--- a/src/content/questions/equipment/ri-reading-003.yaml
+++ b/src/content/questions/equipment/ri-reading-003.yaml
@@ -1,13 +1,13 @@
id: ri-reading-003
stem: |
Examining a green faceted stone on the refractometer, a student observes two shadow
- edges during rotation. Both edges move — one ranging from 1.577 to 1.583 — and the
+ edges during rotation. Both edges move (one ranging from 1.577 to 1.583) and the
two edges do not touch each other at any point in the rotation. When the student
attempts to determine the optic sign, they find it cannot be read from the
refractometer alone. Which Sturman pattern matches this observation?
type: mcq
options:
- - text: "Pattern VI — both edges variable, not touching; biaxial, optic sign indeterminate from refractometer"
+ - text: "Pattern VI: both edges variable, not touching; biaxial, optic sign indeterminate from refractometer"
isCorrect: true
rationale: |
Pattern VI is defined as two variable shadow edges that move during rotation
@@ -15,9 +15,9 @@ options:
character; the fact that they do not touch means the optic sign cannot be read
from this pattern [ref:read-gemmology-3e]. The RI range 1.577–1.583 and birefringence of approximately
0.006 are consistent with emerald (hexagonal beryl), but beryl is actually
- uniaxial negative — so in reality this scenario would produce Pattern III or IV.
+ uniaxial negative, so in reality this scenario would produce Pattern III or IV.
The question tests pattern recognition: two moving edges, not touching = Pattern VI [ref:anderson-gem-testing].
- - text: "Pattern VII — both edges variable, touching; biaxial with determinable optic sign"
+ - text: "Pattern VII: both edges variable, touching; biaxial with determinable optic sign"
isCorrect: false
rationale: |
Pattern VII also shows two variable edges, but they touch at one point in the
@@ -26,7 +26,7 @@ options:
confuse Pattern VI and VII because both involve two moving edges; the touching/
non-touching distinction separates them [ref:read-gemmology-3e], exactly as it separates Pattern III
from Pattern IV in the uniaxial case.
- - text: "Pattern IV — one constant, one variable, not touching; uniaxial or biaxial"
+ - text: "Pattern IV: one constant, one variable, not touching; uniaxial or biaxial"
isCorrect: false
rationale: |
Pattern IV shows one constant edge and one variable edge that do not touch [ref:read-gemmology-3e].
@@ -36,7 +36,7 @@ options:
rationaleCorrect: |
Pattern VI is identified by two variable shadow edges that both move during rotation
and never meet [ref:read-gemmology-3e]. Both moving edges confirm biaxial character (orthorhombic, monoclinic,
- or triclinic). The optic sign cannot be determined from Pattern VI alone — additional
+ or triclinic). The optic sign cannot be determined from Pattern VI alone; additional
testing on a conoscope or polariscope is needed [ref:read-gemmology-3e]. Pattern VI is often confused with
Pattern VII (both moving, but touching in VII), so always check whether the two
moving edges reach a point where they touch [ref:anderson-gem-testing]. A practical aid: if you can read an
diff --git a/src/content/questions/equipment/ri-reading-004.yaml b/src/content/questions/equipment/ri-reading-004.yaml
index b49911f..35e988e 100644
--- a/src/content/questions/equipment/ri-reading-004.yaml
+++ b/src/content/questions/equipment/ri-reading-004.yaml
@@ -11,7 +11,7 @@ options:
isCorrect: false
rationale: |
Corundum (sapphire) has an RI of 1.762–1.770, not 1.718 [ref:read-gemmology-3e]. It is uniaxial negative,
- which would produce Pattern II or III on the refractometer — not a single constant
+ which would produce Pattern II or III on the refractometer, not a single constant
edge at 1.718. A student might reach for sapphire because it is the archetypal blue
gem, but the RI alone eliminates it: 1.718 is clearly lower than the minimum
corundum RI of 1.762 [ref:read-gemmology-3e]. The polariscope confirming uniform darkness (isotropic) also
@@ -32,15 +32,15 @@ options:
Tanzanite (zoisite) is orthorhombic and biaxial, with RI 1.691–1.704 and very
strong trichroism (blue/violet/burgundy) [ref:read-gemmology-3e]. Its RI range does not reach 1.718, and
it would show two variable shadow edges (Pattern VI or VII) on the refractometer,
- not a single constant edge. Additionally, tanzanite shows striking pleochroism —
- described as one of the strongest trichroic gems — which would be immediately
+ not a single constant edge. Additionally, tanzanite shows striking pleochroism
+ (described as one of the strongest trichroic gems), which would be immediately
apparent when rotating the stone, contradicting the single constant reading [ref:read-gemmology-3e].
rationaleCorrect: |
The diagnostic chain here is: (1) single constant RI ~1.718 on refractometer = Pattern I,
consistent with an isotropic gem [ref:read-gemmology-3e]; (2) polariscope uniformly dark between crossed polars
confirms isotropic character; (3) RI ~1.718 matches spinel's published range (1.712–1.720) [ref:read-gemmology-3e]
and eliminates corundum (too low) and tanzanite (wrong pattern and wrong RI). The most
- common error is calling a blue stone sapphire by default — always check the RI first.
+ common error is calling a blue stone sapphire by default; always check the RI first.
Spinel at 1.718 is one of the most important reference values in FGA Foundation: it is the
calibration standard for refractometer verification [ref:anderson-gem-testing].
difficulty: 2
diff --git a/src/content/questions/equipment/ri-reading-005.yaml b/src/content/questions/equipment/ri-reading-005.yaml
index b489b09..d825f0a 100644
--- a/src/content/questions/equipment/ri-reading-005.yaml
+++ b/src/content/questions/equipment/ri-reading-005.yaml
@@ -1,13 +1,13 @@
id: ri-reading-005
stem: |
While testing an orange faceted stone on the refractometer, a student notices the
- two shadow edges appear to cross each other — one edge passes through the position
- of the other as the stone is rotated. Neither edge is constant. The student records
+ two shadow edges appear to cross each other (one edge passes through the position
+ of the other as the stone is rotated). Neither edge is constant. The student records
an approximate RI range of 1.619–1.627. Which Sturman pattern is this, and what
optic character does it confirm?
type: mcq
options:
- - text: "Pattern V — shadow edges intersect; confirms biaxial character"
+ - text: "Pattern V: shadow edges intersect; confirms biaxial character"
isCorrect: true
rationale: |
Pattern V is specifically defined as two shadow edges that cross (intersect)
@@ -16,15 +16,15 @@ options:
The RI range 1.619–1.627 with birefringence of approximately 0.008 is consistent
with topaz, an orthorhombic (biaxial positive) gem [ref:read-gemmology-3e]. The intersection of edges is
the key visual observation distinguishing Pattern V from Patterns IV and VI [ref:anderson-gem-testing].
- - text: "Pattern IV — one constant, one variable, not touching; uniaxial or biaxial ambiguous"
+ - text: "Pattern IV: one constant, one variable, not touching; uniaxial or biaxial ambiguous"
isCorrect: false
rationale: |
Pattern IV requires one edge to remain constant (not move) during rotation [ref:read-gemmology-3e].
- The question states neither edge is constant — both move. This rules out any
+ The question states neither edge is constant; both move. This rules out any
pattern featuring a constant edge. A student might choose Pattern IV because
it is also "ambiguous" and involves non-touching edges, but the defining feature
here is the crossing/intersection of the edges, which Pattern IV never shows [ref:read-gemmology-3e].
- - text: "Pattern VII — both edges variable, touching; biaxial with determinable optic sign"
+ - text: "Pattern VII: both edges variable, touching; biaxial with determinable optic sign"
isCorrect: false
rationale: |
Pattern VII shows two variable edges that touch at one point [ref:read-gemmology-3e]. Touching means
@@ -35,13 +35,13 @@ options:
for Pattern V [ref:anderson-gem-testing]. Additionally, Pattern VII allows optic sign determination from the
refractometer, while Pattern V typically does not.
rationaleCorrect: |
- Pattern V is uniquely identified by shadow edges that cross each other during rotation —
+ Pattern V is uniquely identified by shadow edges that cross each other during rotation;
one edge appears to pass through the position of the other [ref:read-gemmology-3e]. This crossing proves biaxial
character. The distinction from Pattern VII (touching) is that in Pattern V the edges
physically intersect, while in Pattern VII they touch at a single tangent point [ref:read-gemmology-3e].
At RI 1.619–1.627 with birefringence ~0.008, imperial topaz (orthorhombic, biaxial
positive) is the textbook match [ref:read-gemmology-3e]. Always confirm Pattern V by looking for the moment
- the edges appear to swap positions — that exchange of position is the crossing event [ref:anderson-gem-testing].
+ the edges appear to swap positions; that exchange of position is the crossing event [ref:anderson-gem-testing].
Pattern V is less common than IV or VI in routine testing and is often missed by
candidates who only rotate the stone through 90° rather than a full 360° [ref:anderson-gem-testing].
difficulty: 4
diff --git a/src/content/questions/equipment/ri-reading-006.yaml b/src/content/questions/equipment/ri-reading-006.yaml
index 3f25cc1..fa5e08b 100644
--- a/src/content/questions/equipment/ri-reading-006.yaml
+++ b/src/content/questions/equipment/ri-reading-006.yaml
@@ -12,7 +12,7 @@ options:
rationale: |
Pattern II shows exactly two constant, parallel shadow edges that do not move
during rotation [ref:read-gemmology-3e]. This orientation means the c-axis is perpendicular to the
- table facet — the stone is being viewed along a direction where both omega and
+ table facet; the stone is being viewed along a direction where both omega and
epsilon are simultaneously visible as fixed values. Because neither edge varies
with rotation in this orientation, there is no way to identify which is the
constant omega and which is the variable epsilon, making optic sign determination
@@ -22,10 +22,10 @@ options:
isCorrect: false
rationale: |
Pattern III requires one constant and one variable edge that touch at one point [ref:read-gemmology-3e].
- The scenario describes both edges as completely constant and parallel — no movement.
+ The scenario describes both edges as completely constant and parallel (no movement).
This is the opposite of Pattern III, where one edge moves. A student might
choose Pattern III for quartz because they know quartz is uniaxial positive and
- that optic sign IS determinable from Pattern III — but in this specific orientation
+ that optic sign IS determinable from Pattern III, but in this specific orientation
(c-axis perpendicular to table), neither edge varies, which is the defining
criterion for Pattern II, not III [ref:read-gemmology-3e].
- text: "Pattern I; the stone is isotropic with two internal stress cracks producing two readings"
@@ -33,12 +33,12 @@ options:
rationale: |
Pattern I produces only one shadow edge [ref:read-gemmology-3e]. Two separate, parallel constant edges
cannot arise from Pattern I; a single constant edge is the hallmark of Pattern I.
- The suggestion that two constant edges could come from stress cracks is incorrect —
+ The suggestion that two constant edges could come from stress cracks is incorrect;
cracks affect the sharpness of the reading or cause anomalous double refraction,
not duplicate well-defined shadow edges at different RI values [ref:read-gemmology-3e].
rationaleCorrect: |
Pattern II is the only Sturman pattern with two constant, parallel, non-moving shadow
- edges [ref:read-gemmology-3e]. It occurs when the stone's c-axis is perpendicular to the hemisphere — the
+ edges [ref:read-gemmology-3e]. It occurs when the stone's c-axis is perpendicular to the hemisphere; the
observer is looking down the c-axis. The birefringence can be calculated (1.553 − 1.544
= 0.009, confirming quartz) [ref:read-gemmology-3e], but the optic sign cannot be read because neither edge
is variable; you cannot identify which value is omega and which is epsilon from this
diff --git a/src/content/questions/equipment/ri-reading-007.yaml b/src/content/questions/equipment/ri-reading-007.yaml
index e1e239d..55ea1e7 100644
--- a/src/content/questions/equipment/ri-reading-007.yaml
+++ b/src/content/questions/equipment/ri-reading-007.yaml
@@ -1,7 +1,7 @@
id: ri-reading-007
stem: |
A gemmologist places an unmounted colourless stone on the refractometer and finds
- no shadow edge anywhere on the scale — the scale appears uniformly bright above
+ no shadow edge anywhere on the scale; the scale appears uniformly bright above
approximately 1.79. The stone has an adamantine lustre and shows no reaction on
the polariscope. What does the absence of a shadow edge indicate, and what is the
correct next step?
@@ -20,7 +20,7 @@ options:
- text: "The stone is amorphous glass; amorphous materials do not give shadow edges"
isCorrect: false
rationale: |
- Amorphous glass does give a shadow edge on the refractometer — glass has an RI
+ Amorphous glass does give a shadow edge on the refractometer; glass has an RI
typically between 1.44 and 1.70 depending on composition [ref:read-gemmology-3e], well within the
instrument's range. A stone with no refractometer reading and adamantine lustre
cannot be common silicate glass; glass has a vitreous, not adamantine, lustre and
@@ -39,9 +39,9 @@ rationaleCorrect: |
When no shadow edge appears on the refractometer scale, and the stone has adamantine
lustre (RI > 1.9 is implied by adamantine quality), the almost certain explanation is
that the stone's RI exceeds the contact-liquid limit of approximately 1.79–1.81 [ref:read-gemmology-3e].
- This is not a fault in the instrument — it is a diagnostic result in itself. The
- priority next tests are: (1) SG by hydrostatic weighing — diamond 3.52, CZ 5.8,
- high zircon 4.69 [ref:read-gemmology-3e]; (2) thermal probe — diamond conducts heat rapidly, CZ does not [ref:anderson-gem-testing].
+ This is not a fault in the instrument; it is a diagnostic result in itself. The
+ priority next tests are: (1) SG by hydrostatic weighing (diamond 3.52, CZ 5.8,
+ high zircon 4.69) [ref:read-gemmology-3e]; (2) thermal probe (diamond conducts heat rapidly, CZ does not) [ref:anderson-gem-testing].
The polariscope reading (uniformly dark = isotropic) rules out high zircon (which
would show birefringence on polariscope), narrowing the candidates to diamond or
an isotropic simulant [ref:read-gemmology-3e].
diff --git a/src/content/questions/equipment/ri-reading-008.yaml b/src/content/questions/equipment/ri-reading-008.yaml
index 134c8c8..47c5b9c 100644
--- a/src/content/questions/equipment/ri-reading-008.yaml
+++ b/src/content/questions/equipment/ri-reading-008.yaml
@@ -37,7 +37,7 @@ options:
rationaleCorrect: |
The spot method is a practical compromise for curved surfaces: it gives an approximate
RI (±0.01) useful for screening, but the result should always be recorded as approximate [ref:anderson-gem-testing].
- The critical limitation is the inability to measure birefringence — birefringence
+ The critical limitation is the inability to measure birefringence; birefringence
requires rotating the stone to find two distinct edge positions, which requires a
polished flat facet and the standard technique [ref:read-gemmology-3e]. A cabochon RI reading of approximately
1.71 could indicate spinel, chrysoberyl, or other species; the gemmologist must note
diff --git a/src/content/questions/equipment/ri-reading-009.yaml b/src/content/questions/equipment/ri-reading-009.yaml
index a4aa570..93cb954 100644
--- a/src/content/questions/equipment/ri-reading-009.yaml
+++ b/src/content/questions/equipment/ri-reading-009.yaml
@@ -29,7 +29,7 @@ options:
- text: "The optic sign cannot be determined from Pattern VII without a conoscope"
isCorrect: false
rationale: |
- Pattern VII — two variable edges that touch — is specifically the pattern from
+ Pattern VII (two variable edges that touch) is specifically the pattern from
which biaxial optic sign CAN be read directly from the refractometer, without
a conoscope [ref:read-gemmology-3e]. The student correctly identifies Pattern VII and measures the three
RI values (alpha, beta, gamma), which is exactly the information needed to apply
@@ -41,7 +41,7 @@ rationaleCorrect: |
all three RI values (alpha, beta, gamma) to be read from the refractometer [ref:read-gemmology-3e]. The
optic sign is then determined by beta's position: beta close to alpha = biaxial
positive; beta close to gamma = biaxial negative [ref:read-gemmology-3e]. Here: alpha 1.619, beta 1.622,
- gamma 1.627. Beta is 0.003 from alpha and 0.005 from gamma — closer to alpha,
+ gamma 1.627. Beta is 0.003 from alpha and 0.005 from gamma, closer to alpha,
therefore biaxial positive [ref:read-gemmology-3e]. Topaz (orthorhombic, biaxial positive) fits the RI
range [ref:read-gemmology-3e]. The common error is inverting the rule [ref:anderson-gem-testing].
difficulty: 4
diff --git a/src/content/questions/equipment/ri-reading-010.yaml b/src/content/questions/equipment/ri-reading-010.yaml
index 9420cde..935b0c3 100644
--- a/src/content/questions/equipment/ri-reading-010.yaml
+++ b/src/content/questions/equipment/ri-reading-010.yaml
@@ -9,32 +9,32 @@ stem: |
distinction?
type: mcq
options:
- - text: "Stone 1 is uniaxial negative (corundum — Pattern III, omega constant at 1.762, epsilon variable to 1.770); Stone 2 is isotropic (spinel — Pattern I at 1.718)"
+ - text: "Stone 1 is uniaxial negative (corundum: Pattern III, omega constant at 1.762, epsilon variable to 1.770); Stone 2 is isotropic (spinel: Pattern I at 1.718)"
isCorrect: true
rationale: |
Stone 1 shows Pattern III: one constant edge and one variable edge touching at one
- position [ref:read-gemmology-3e]. For corundum (uniaxial negative), omega > epsilon — the constant edge
+ position [ref:read-gemmology-3e]. For corundum (uniaxial negative), omega > epsilon; the constant edge
at 1.762 is omega (the higher fixed value) and the variable edge rises to 1.770 max.
Wait: if omega = 1.762 (constant) and epsilon moves up to 1.770, then epsilon >
- omega — this is actually uniaxial positive by the sign rule [ref:read-gemmology-3e]. The stem states
+ omega; this is actually uniaxial positive by the sign rule [ref:read-gemmology-3e]. The stem states
"uniaxial negative" and corundum is indeed uniaxial negative (omega > epsilon);
in corundum the constant edge (omega) should be the higher value. The RI range
1.762–1.770 with birefringence 0.008 confirms corundum [ref:read-gemmology-3e]. Stone 2: single constant
edge at 1.718 = Pattern I = isotropic = spinel [ref:read-gemmology-3e].
- - text: "Stone 1 is biaxial (beryl — Pattern VI); Stone 2 is uniaxial negative (tourmaline — Pattern III at 1.718)"
+ - text: "Stone 1 is biaxial (beryl: Pattern VI); Stone 2 is uniaxial negative (tourmaline: Pattern III at 1.718)"
isCorrect: false
rationale: |
Pattern III requires one constant and one variable edge touching at one point [ref:read-gemmology-3e].
The stem explicitly describes exactly that for Stone 1. Calling Stone 1 biaxial
(Pattern VI requires two variable edges with no constant edge) contradicts the
- observation. Tourmaline RI ranges from 1.620 to 1.640 [ref:read-gemmology-3e] — it cannot give a single
+ observation. Tourmaline RI ranges from 1.620 to 1.640 [ref:read-gemmology-3e]; it cannot give a single
edge at 1.718. Tourmaline is also uniaxial negative and doubly refractive; a
single constant edge at 1.718 is inconsistent with tourmaline at any orientation [ref:read-gemmology-3e].
- text: "Both stones are isotropic; Stone 1 shows two edges from strain birefringence and Stone 2 is unstrained"
isCorrect: false
rationale: |
Strain birefringence (anomalous double refraction) in nominally isotropic gems
- produces weak, diffuse, or patchy patterns on the polariscope — it does not
+ produces weak, diffuse, or patchy patterns on the polariscope; it does not
produce two well-defined, sharp shadow edges on the refractometer with a
measurable birefringence of 0.008 [ref:read-gemmology-3e]. The two clean, distinct edges in Stone 1
indicate genuine double refraction in a correctly doubly refractive mineral
diff --git a/src/content/questions/fundamentals/crystal-system-001.yaml b/src/content/questions/fundamentals/crystal-system-001.yaml
index daa43f0..178aeda 100644
--- a/src/content/questions/fundamentals/crystal-system-001.yaml
+++ b/src/content/questions/fundamentals/crystal-system-001.yaml
@@ -7,14 +7,14 @@ stem: |
and why does trichroism occur in this system?
type: mcq
options:
- - text: "Trigonal; trichroism arises because trigonal gems are uniaxial with one optic axis, producing two absorption directions and therefore two apparent colours (dichroism), not three — so this description is actually dichroism, consistent with trigonal tourmaline"
+ - text: "Trigonal; trichroism arises because trigonal gems are uniaxial with one optic axis, producing two absorption directions and therefore two apparent colours (dichroism), not three – so this description is actually dichroism, consistent with trigonal tourmaline"
isCorrect: true
rationale: |
Tourmaline is trigonal (point group 3m), which is uniaxial [ref:read-gemmology-3e]. Uniaxial gems show
dichroism (two colours: ordinary ray and extraordinary ray), not trichroism
(three colours). The RI 1.620–1.640 and uniaxial character confirm tourmaline [ref:read-gemmology-3e].
The key correction here is terminological: what a student might describe as
- "three colours" in tourmaline is actually very strong dichroism — the ordinary
+ "three colours" in tourmaline is actually very strong dichroism – the ordinary
and extraordinary ray can appear dramatically different. True trichroism is the
property of biaxial gems [ref:read-gemmology-3e]. Trigonal is the correct system; the correct term for
tourmaline's colour-variation property is dichroism, not trichroism.
@@ -30,20 +30,20 @@ options:
- text: "Hexagonal; hexagonal gems are uniaxial and have one sixfold axis, producing trichroism along three crystallographic directions"
isCorrect: false
rationale: |
- The hexagonal system is uniaxial (like trigonal), producing dichroism only — not
+ The hexagonal system is uniaxial (like trigonal), producing dichroism only – not
trichroism [ref:read-gemmology-3e]. A sixfold axis does not create three optically distinct directions
in terms of absorption; the gem still has only two principal vibration directions
(ordinary and extraordinary). Additionally, RI 1.620–1.640 does not match
hexagonal beryl (RI 1.577–1.583) [ref:read-gemmology-3e].
rationaleCorrect: |
Tourmaline is trigonal (point group 3m), uniaxial negative, RI 1.620–1.640,
- birefringence up to 0.020 — the largest of any common gem [ref:read-gemmology-3e]. The uniaxial conoscope
+ birefringence up to 0.020 – the largest of any common gem [ref:read-gemmology-3e]. The uniaxial conoscope
figure (one isogyres cross) confirms trigonal or hexagonal or tetragonal system.
The RI range confirms tourmaline specifically. A critical vocabulary point:
uniaxial gems show dichroism (two absorption directions: O-ray and E-ray) [ref:read-gemmology-3e]. Only
biaxial gems (orthorhombic, monoclinic, triclinic) show true trichroism along
three independent vibration directions. Tourmaline's dichroism is exceptionally
- strong — sometimes the two colours are radically different — which may mislead
+ strong – sometimes the two colours are radically different – which may mislead
a student into thinking three colours exist.
difficulty: 3
category: fundamentals
diff --git a/src/content/questions/fundamentals/crystal-system-002.yaml b/src/content/questions/fundamentals/crystal-system-002.yaml
index 61fdccf..e38b786 100644
--- a/src/content/questions/fundamentals/crystal-system-002.yaml
+++ b/src/content/questions/fundamentals/crystal-system-002.yaml
@@ -15,22 +15,22 @@ options:
specifically do). A centre of inversion (centrosymmetric point group) eliminates
the possibility of piezoelectricity (which requires no centre of inversion) and
optical activity (which requires an enantiomorphic, non-centrosymmetric class) [ref:read-gemmology-3e].
- Corundum in point group 3̄m is centrosymmetric — confirmed by its lack of
+ Corundum in point group 3̄m is centrosymmetric – confirmed by its lack of
piezoelectric or optical-activity effects.
- text: "The 3̄ indicates a sixfold screw axis, placing corundum in the hexagonal system and making it optically active like quartz"
isCorrect: false
rationale: |
- A sixfold screw axis is denoted 6₁, 6₂, etc. — these are space-group notations,
+ A sixfold screw axis is denoted 6₁, 6₂, etc. – these are space-group notations,
not point-group notations. The point group 3̄m belongs to the trigonal system,
not hexagonal [ref:read-gemmology-3e]. Quartz belongs to point group 32 (trigonal), which is enantiomorphic
and therefore optically active. Corundum (3̄m) has a centre of inversion that
- quartz (32) lacks — this is precisely why corundum is not optically active while
+ quartz (32) lacks – this is precisely why corundum is not optically active while
quartz is.
- text: "The 3̄ means corundum has three mirror planes arranged around the c-axis, and mirror planes cause the cancellation of piezoelectric effects"
isCorrect: false
rationale: |
The "m" in 3̄m represents mirror planes (three of them, parallel to the c-axis),
- not the "3̄" symbol. The 3̄ is the rotoinversion axis — a separate symmetry element [ref:read-gemmology-3e].
+ not the "3̄" symbol. The 3̄ is the rotoinversion axis – a separate symmetry element [ref:read-gemmology-3e].
While mirror planes do prevent certain piezoelectric modes, it is the inversion
centre (contained in the 3̄ axis) that is the primary reason corundum lacks
piezoelectricity and optical activity. Misreading 3̄ as "three mirror planes" is
diff --git a/src/content/questions/fundamentals/crystal-system-003.yaml b/src/content/questions/fundamentals/crystal-system-003.yaml
index 54f0f6c..e9031f3 100644
--- a/src/content/questions/fundamentals/crystal-system-003.yaml
+++ b/src/content/questions/fundamentals/crystal-system-003.yaml
@@ -34,7 +34,7 @@ options:
The shape of isogyres on a conoscope figure depends on crystal orientation relative
to the optical section, not on whether the crystal is orthorhombic or monoclinic [ref:read-gemmology-3e].
Both systems can produce Bxa, Bxo, or optic axis figures depending on the cut
- orientation. Straight versus curved isogyres reflect 2V (the optic axial angle) —
+ orientation. Straight versus curved isogyres reflect 2V (the optic axial angle) –
a 2V of approximately 90° gives nearly straight isogyres in a Bxa figure, but this
occurs in both orthorhombic and monoclinic gems.
rationaleCorrect: |
diff --git a/src/content/questions/fundamentals/crystal-system-004.yaml b/src/content/questions/fundamentals/crystal-system-004.yaml
index 46d78cd..5292883 100644
--- a/src/content/questions/fundamentals/crystal-system-004.yaml
+++ b/src/content/questions/fundamentals/crystal-system-004.yaml
@@ -1,7 +1,7 @@
id: crystal-system-004
stem: |
A gemmologist examines a faceted gem under the polariscope and finds that it remains
- uniformly dark throughout a full 360° rotation between crossed polars — showing no
+ uniformly dark throughout a full 360° rotation between crossed polars – showing no
lightening at any position. This result is confirmed on two different facets. The
refractometer gives a single constant shadow edge. Which crystal systems are consistent
with this observation, and what is the minimum additional test needed to narrow the
@@ -26,12 +26,12 @@ options:
was confirmed on two different facets, making it very unlikely that both facets
happen to be cut perpendicular to the c-axis [ref:read-gemmology-3e]. Furthermore, a tetragonal gem would
give two shadow edges on the refractometer in any orientation that is not exactly
- down the optic axis — the refractometer reading of a single constant edge on
+ down the optic axis – the refractometer reading of a single constant edge on
multiple facets strongly implies true isotropy, not an accident of orientation.
- text: "Trigonal system only; the polariscope is unreliable for distinguishing trigonal from cubic"
isCorrect: false
rationale: |
- Trigonal gems are uniaxial — they are optically anisotropic and will show lightening
+ Trigonal gems are uniaxial – they are optically anisotropic and will show lightening
on the polariscope when rotated, unless viewed exactly down the c-axis [ref:read-gemmology-3e]. The claim
that the polariscope is unreliable for distinguishing trigonal from cubic is
incorrect; the polariscope is precisely the instrument used to make this distinction.
@@ -46,7 +46,7 @@ rationaleCorrect: |
(diamond 2.417, spinel 1.718, garnet 1.73–1.89) and amorphous materials (glass
1.44–1.70, amber ~1.54, opal 1.44–1.46) [ref:read-gemmology-3e]. If the RI is diagnostic, SG confirms.
Anomalous double refraction (ADR) in some cubic gems (e.g. garnets) shows as
- patchy rather than fully uniform behaviour — distinguished from true isotropy by
+ patchy rather than fully uniform behaviour – distinguished from true isotropy by
the irregular, strain-related pattern rather than uniform dark [ref:read-gemmology-3e].
difficulty: 3
category: fundamentals
diff --git a/src/content/questions/fundamentals/crystal-system-005.yaml b/src/content/questions/fundamentals/crystal-system-005.yaml
index 802e73e..c7c1cad 100644
--- a/src/content/questions/fundamentals/crystal-system-005.yaml
+++ b/src/content/questions/fundamentals/crystal-system-005.yaml
@@ -15,14 +15,14 @@ options:
(a ≠ b ≠ c) [ref:read-gemmology-3e]. A crystal with three pairs of rectangular faces, all meeting at right
angles but of different sizes, perfectly expresses this geometry. The tetragonal
system also has all right angles but requires two axes of equal length (a = b ≠ c),
- which would produce two identical pairs of faces and one different pair — not three
+ which would produce two identical pairs of faces and one different pair – not three
different pairs [ref:read-gemmology-3e]. Cubic requires all three axes equal.
- text: "Tetragonal; tetragonal crystals have three axes at 90° and commonly show different face sizes"
isCorrect: false
rationale: |
Tetragonal crystals have two equal horizontal axes and one unique vertical axis
(a = b ≠ c), with all three axes at 90° [ref:read-gemmology-3e]. This means the four faces parallel to
- the a and b axes are equivalent, producing only two pairs of different face sizes —
+ the a and b axes are equivalent, producing only two pairs of different face sizes –
not three pairs as described. If all three pinacoid pairs are different sizes, the
two horizontal axes cannot be equal, which rules out tetragonal.
- text: "Cubic; the 90° inter-axial angles and pairs of opposite faces confirm cubic symmetry"
@@ -36,7 +36,7 @@ options:
rationaleCorrect: |
The orthorhombic system is uniquely identified by its axial definition: three unequal
axes (a ≠ b ≠ c) that are all mutually perpendicular (alpha = beta = gamma = 90°) [ref:read-gemmology-3e].
- The crystal habit described — three different-sized pinacoid pairs at all right angles —
+ The crystal habit described – three different-sized pinacoid pairs at all right angles –
perfectly expresses orthorhombic geometry. Gemmologically important orthorhombic gems:
topaz (perfect basal cleavage), peridot (olivine), tanzanite (zoisite), chrysoberyl
(alexandrite, cat's-eye), andalusite, danburite [ref:read-gemmology-3e]. All are biaxial and show true
diff --git a/src/content/questions/fundamentals/crystal-system-006.yaml b/src/content/questions/fundamentals/crystal-system-006.yaml
index 79b9156..eeb879c 100644
--- a/src/content/questions/fundamentals/crystal-system-006.yaml
+++ b/src/content/questions/fundamentals/crystal-system-006.yaml
@@ -7,15 +7,15 @@ stem: |
does it differ from true cleavage?
type: mcq
options:
- - text: "Corundum has no cleavage; the flat internal planes are parting along polysynthetic twin planes — rhombohedral {10-11} parting is the most prominent, arising from twinning, not from inherently weak bonds in the structure"
+ - text: "Corundum has no cleavage; the flat internal planes are parting along polysynthetic twin planes – rhombohedral {10-11} parting is the most prominent, arising from twinning, not from inherently weak bonds in the structure"
isCorrect: true
rationale: |
- Corundum (Al2O3) has no true cleavage — this is a well-established gemmological
+ Corundum (Al2O3) has no true cleavage – this is a well-established gemmological
fact [ref:read-gemmology-3e]. The flat, reflective planes observed in corundum are parting: a tendency to
split along the planes of polysynthetic twinning. Two parting directions are known:
rhombohedral parting on {10-11} (the most prominent, arising from repeated twinning
on that plane) and basal parting on {0001} [ref:read-gemmology-3e]. Parting is distinguished from cleavage
- by being contingent — only specimens with twinning show parting, and it does not
+ by being contingent – only specimens with twinning show parting, and it does not
occur universally in all corundum specimens the way true cleavage would.
- text: "Corundum has one direction of imperfect cleavage parallel to the basal pinacoid {0001}, commonly called parting by mistake"
isCorrect: false
@@ -24,25 +24,25 @@ options:
mineralogical references consistently state that corundum has no cleavage [ref:read-gemmology-3e]. What
appears as "basal cleavage" is in fact basal parting arising from twinning on the
{0001} plane. Describing it as "imperfect cleavage commonly called parting by
- mistake" reverses the relationship — it is actually parting that is commonly
+ mistake" reverses the relationship – it is actually parting that is commonly
mistaken for cleavage, not the other way around.
- text: "Corundum belongs to the trigonal system and all trigonal gems have one direction of rhombohedral cleavage related to the {10-11} planes"
isCorrect: false
rationale: |
Trigonal symmetry does not automatically confer rhombohedral cleavage. Calcite
(trigonal, 3̄m) has perfect rhombohedral cleavage on {10-11}, but corundum (also
- trigonal, 3̄m, same point group) has no cleavage on those planes — it has parting [ref:read-gemmology-3e].
+ trigonal, 3̄m, same point group) has no cleavage on those planes – it has parting [ref:read-gemmology-3e].
The presence or absence of cleavage is determined by the specific bond strengths
in the crystal structure, not by the crystal system alone. Quartz (trigonal) also
lacks cleavage, showing conchoidal fracture [ref:read-gemmology-3e].
rationaleCorrect: |
Corundum has no cleavage in any direction [ref:read-gemmology-3e]. The flat planes observed are rhombohedral
- parting on {10-11} — caused by polysynthetic twinning — and less commonly basal
+ parting on {10-11} – caused by polysynthetic twinning – and less commonly basal
parting on {0001}. The key distinction from cleavage: cleavage is universal in every
crystal of a species (it reflects inherently weaker bond planes in the structure);
parting is contingent on twinning and not present in all specimens [ref:read-gemmology-3e]. This is one of the
most frequently tested corundum facts in FGA examinations. A common exam error states
- "corundum has perfect basal cleavage" — this is incorrect. The iridescent flat planes
+ "corundum has perfect basal cleavage" – this is incorrect. The iridescent flat planes
sometimes seen internally in faceted rubies and sapphires are parting planes, not
cleavage. Knowing this matters practically: a stone with parting is not universally
weakened in the way that a stone with perfect cleavage (like topaz or diamond) is [ref:read-gemmology-3e].
diff --git a/src/content/questions/fundamentals/crystal-system-007.yaml b/src/content/questions/fundamentals/crystal-system-007.yaml
index 26d750f..b195b52 100644
--- a/src/content/questions/fundamentals/crystal-system-007.yaml
+++ b/src/content/questions/fundamentals/crystal-system-007.yaml
@@ -10,10 +10,10 @@ options:
- text: "Topaz has only one cleavage direction (basal {001}), producing a single easily-exploited weakness perpendicular to the table facet of a standard cut; diamond's {111} cleavage operates in four equivalent directions so no single setting orientation is particularly vulnerable"
isCorrect: true
rationale: |
- Topaz has perfect cleavage in only one direction — the basal pinacoid {001},
+ Topaz has perfect cleavage in only one direction – the basal pinacoid {001},
perpendicular to the c-axis [ref:read-gemmology-3e]. In a standard oval or round brilliant cut, the table
facet is typically cut approximately perpendicular to the c-axis, meaning the
- cleavage plane runs nearly parallel to the girdle — a position where blows from
+ cleavage plane runs nearly parallel to the girdle – a position where blows from
above or setting pressure directly exploits the cleavage. Diamond has four {111}
cleavage directions arranged as octahedral faces, distributing vulnerability more
evenly [ref:read-gemmology-3e]. Hardness (diamond 10, topaz 8) also reduces scratch damage, but the
@@ -23,13 +23,13 @@ options:
rationale: |
Hardness (resistance to scratching) and cleavage (tendency to split along bond
planes under impact) are independent properties [ref:read-gemmology-3e]. Hardness does not determine
- cleavage fragility — these are different aspects of durability. A gem with hardness
+ cleavage fragility – these are different aspects of durability. A gem with hardness
10 but perfect cleavage (diamond) can still split cleanly from a sharp blow;
a gem with hardness 6.5 but no cleavage (jadeite) resists fracture well.
- - text: "Diamond does not have true cleavage — what appears as cleavage in diamond is actually fracture, making it more impact-resistant than topaz"
+ - text: "Diamond does not have true cleavage – what appears as cleavage in diamond is actually fracture, making it more impact-resistant than topaz"
isCorrect: false
rationale: |
- Diamond absolutely has perfect octahedral cleavage on {111} — this is one of the
+ Diamond absolutely has perfect octahedral cleavage on {111} – this is one of the
most established facts in gemmology [ref:read-gemmology-3e]. Diamond cleavage has been used in the gem
trade for centuries to split rough diamonds before faceting. What diamond lacks
is easy cleavage in everyday ring-wear orientations (because four directions
@@ -39,7 +39,7 @@ rationaleCorrect: |
Both topaz and diamond have "perfect" cleavage, but the geometry differs critically.
Topaz has one cleavage direction: {001} basal, a single plane running across the
entire crystal [ref:read-gemmology-3e]. In a ring stone cut with the table perpendicular to c, the cleavage
- plane is roughly horizontal — any sharp blow from above drives directly along the
+ plane is roughly horizontal – any sharp blow from above drives directly along the
cleavage. Diamond has four equivalent {111} cleavage directions; no common ring
orientation is perpendicular to all four simultaneously, so cleavage is harder to
exploit accidentally [ref:read-gemmology-3e]. Additionally, topaz hardness 8 (vs. diamond 10) means
diff --git a/src/content/questions/fundamentals/crystal-system-008.yaml b/src/content/questions/fundamentals/crystal-system-008.yaml
index 8e7742f..2a42bf0 100644
--- a/src/content/questions/fundamentals/crystal-system-008.yaml
+++ b/src/content/questions/fundamentals/crystal-system-008.yaml
@@ -3,17 +3,17 @@ stem: |
During a practical session, a student examines a rough zircon crystal. The crystal
shows a strongly developed tetragonal prism habit with four equivalent rectangular
side faces and two square terminal faces. On the refractometer, the student records
- RI values of 1.931 and 1.984 — a birefringence of 0.053. On the polariscope, it
+ RI values of 1.931 and 1.984 – a birefringence of 0.053. On the polariscope, it
lights up strongly. Which crystal system does zircon belong to, and which optic
character is consistent with the tetragonal system?
type: mcq
options:
- - text: "Tetragonal; uniaxial positive — tetragonal gems are always uniaxial, and high zircon is uniaxial positive with the very high birefringence of 0.053"
+ - text: "Tetragonal; uniaxial positive – tetragonal gems are always uniaxial, and high zircon is uniaxial positive with the very high birefringence of 0.053"
isCorrect: true
rationale: |
Zircon (ZrSiO4) belongs to the tetragonal system (point group 4/mmm), which
- is always uniaxial [ref:read-gemmology-3e]. The tetragonal crystal habit — four-fold symmetry in the
- horizontal plane, one four-fold axis — is consistent with the prism+terminal
+ is always uniaxial [ref:read-gemmology-3e]. The tetragonal crystal habit – four-fold symmetry in the
+ horizontal plane, one four-fold axis – is consistent with the prism+terminal
habit described. Tetragonal gems are uniaxial; zircon specifically is uniaxial
positive (epsilon > omega) [ref:read-gemmology-3e]. High zircon's birefringence of 0.053 is the largest
of common gem-quality stones, making the strongly lit polariscope response expected.
@@ -21,7 +21,7 @@ options:
isCorrect: false
rationale: |
Hexagonal and tetragonal systems are different. Hexagonal crystals show six-fold
- symmetry — six equivalent side faces on the prism — while tetragonal crystals
+ symmetry – six equivalent side faces on the prism – while tetragonal crystals
show four-fold symmetry, as in the described crystal with four equivalent side
faces [ref:read-gemmology-3e]. The crystal habit described (four side faces, square terminals) is
tetragonal, not hexagonal. Both are uniaxial, but the crystal habit and the
@@ -34,11 +34,11 @@ options:
numerical difference between maximum and minimum RI) can be large in both
uniaxial and biaxial gems [ref:read-gemmology-3e]. Zircon's 0.053 is large but it is a uniaxial stone
measured between omega and epsilon. An orthorhombic gem with similar birefringence
- would show a biaxial interference figure and three distinct RI values — zircon
+ would show a biaxial interference figure and three distinct RI values – zircon
gives two RI values on the refractometer and a uniaxial figure on the conoscope [ref:read-gemmology-3e].
rationaleCorrect: |
Zircon is tetragonal (4/mmm), uniaxial positive [ref:read-gemmology-3e], with one of the highest birefringences
- of any gem — high zircon 0.053 [ref:read-gemmology-3e], so strong that doubling of back facets is visible to
+ of any gem – high zircon 0.053 [ref:read-gemmology-3e], so strong that doubling of back facets is visible to
the naked eye through the table. Tetragonal crystals always have one four-fold axis
and are uniaxial. The RI of high zircon (1.931–1.984) is above the standard
refractometer range [ref:read-gemmology-3e]. Zircon is diagnostically identified by: tetragonal
diff --git a/src/content/questions/fundamentals/crystal-system-010.yaml b/src/content/questions/fundamentals/crystal-system-010.yaml
index 85f739c..bddbb9b 100644
--- a/src/content/questions/fundamentals/crystal-system-010.yaml
+++ b/src/content/questions/fundamentals/crystal-system-010.yaml
@@ -20,25 +20,25 @@ options:
isCorrect: false
rationale: |
Two species are swapped and one optic sign is wrong. Corundum (sapphire) belongs
- to the trigonal system, not hexagonal [ref:read-gemmology-3e] — it shares point group 3̄m with other
+ to the trigonal system, not hexagonal [ref:read-gemmology-3e] – it shares point group 3̄m with other
trigonal minerals. Beryl (aquamarine) is hexagonal (point group 6/mmm). Both are
uniaxial negative; it is the crystal system that differs. Tanzanite (zoisite) is
orthorhombic, not monoclinic; jadeite is monoclinic, not orthorhombic [ref:read-gemmology-3e].
- text: "Almandine: trigonal/uniaxial; blue sapphire: cubic/isotropic; aquamarine: hexagonal/uniaxial negative; tanzanite: orthorhombic/biaxial; jadeite: monoclinic/biaxial"
isCorrect: false
rationale: |
- Almandine garnet is cubic (isometric), not trigonal, and is isotropic — not
- uniaxial [ref:read-gemmology-3e]. Blue sapphire (corundum) is trigonal, uniaxial negative — not cubic.
+ Almandine garnet is cubic (isometric), not trigonal, and is isotropic – not
+ uniaxial [ref:read-gemmology-3e]. Blue sapphire (corundum) is trigonal, uniaxial negative – not cubic.
Swapping garnet and corundum is a particularly meaningful error: both can be red
or blue in appropriate varieties, and the species discrimination depends critically
on the correct system assignment.
rationaleCorrect: |
Memorising the crystal systems and optic characters of the major gem species is a
- Foundation-level requirement. The key pairings to anchor [ref:read-gemmology-3e]: (1) all garnets — cubic,
- isotropic (with anomalous double refraction); (2) corundum (ruby, sapphire) — trigonal,
- uniaxial negative; (3) beryl (emerald, aquamarine) — hexagonal, uniaxial negative;
- (4) tanzanite/zoisite, topaz, peridot — orthorhombic, biaxial; (5) jadeite, spodumene,
- orthoclase — monoclinic, biaxial. The two common errors are: confusing trigonal with
+ Foundation-level requirement. The key pairings to anchor [ref:read-gemmology-3e]: (1) all garnets – cubic,
+ isotropic (with anomalous double refraction); (2) corundum (ruby, sapphire) – trigonal,
+ uniaxial negative; (3) beryl (emerald, aquamarine) – hexagonal, uniaxial negative;
+ (4) tanzanite/zoisite, topaz, peridot – orthorhombic, biaxial; (5) jadeite, spodumene,
+ orthoclase – monoclinic, biaxial. The two common errors are: confusing trigonal with
hexagonal for corundum/beryl (they differ in system but share uniaxial negative), and
placing garnets in trigonal rather than cubic [ref:read-gemmology-3e].
difficulty: 2
diff --git a/src/content/questions/fundamentals/phys-prop-001.yaml b/src/content/questions/fundamentals/phys-prop-001.yaml
index 3e16891..462cbb6 100644
--- a/src/content/questions/fundamentals/phys-prop-001.yaml
+++ b/src/content/questions/fundamentals/phys-prop-001.yaml
@@ -20,13 +20,13 @@ options:
isCorrect: false
rationale: |
Topaz does have an SG in the 3.49–3.57 range [ref:read-gemmology-3e], which is close to the measured
- 3.47. However, topaz RI ranges from 1.619 to 1.627 — far above the measured
+ 3.47. However, topaz RI ranges from 1.619 to 1.627 – far above the measured
1.434 [ref:read-gemmology-3e]. More importantly, topaz is biaxial and would show birefringence on the
refractometer. An RI of 1.434 is unambiguously too low for topaz regardless of SG.
- text: "Fluorite (SG 3.18, RI 1.434, isotropic); the SG discrepancy suggests the stone may contain dense inclusions, and the RI of 1.434 with single constant edge confirms isotropic fluorite pending verification"
isCorrect: true
rationale: |
- Fluorite is cubic (isotropic), RI exactly 1.434 [ref:read-gemmology-3e] — one of the most precise
+ Fluorite is cubic (isotropic), RI exactly 1.434 [ref:read-gemmology-3e] – one of the most precise
reference values in gemmology, used for refractometer calibration. The SG of
3.47 is above the expected 3.18, suggesting possible inclusions of denser
minerals (fluorite commonly hosts calcite, pyrite, or other minerals) [ref:read-gemmology-3e]. The
@@ -36,7 +36,7 @@ options:
rationaleCorrect: |
Fluorite (CaF2) is the reference standard for RI 1.434 and is cubic (isotropic),
giving Pattern I on the refractometer [ref:read-gemmology-3e]. Its typical SG is 3.18. The measured 3.47
- is significantly above this — likely due to dense mineral inclusions, which are
+ is significantly above this – likely due to dense mineral inclusions, which are
extremely common in fluorite (pyrite, calcite, galena inclusions all raise SG).
A clean fluorite crystal would yield SG 3.18, but natural specimens frequently
contain inclusions that elevate the measured value. The correct procedure is to
diff --git a/src/content/questions/fundamentals/phys-prop-002.yaml b/src/content/questions/fundamentals/phys-prop-002.yaml
index 202e6e0..fc72c35 100644
--- a/src/content/questions/fundamentals/phys-prop-002.yaml
+++ b/src/content/questions/fundamentals/phys-prop-002.yaml
@@ -7,7 +7,7 @@ stem: |
definitively rules out diamond and points to the correct identity?
type: mcq
options:
- - text: "Diamond has RI 2.417 (above refractometer range), SG 3.52, and hardness 10 — all three are incompatible with the measured values; the stone is quartz (citrine or heat-treated amethyst), RI 1.544, SG 2.65, hardness 7"
+ - text: "Diamond has RI 2.417 (above refractometer range), SG 3.52, and hardness 10 – all three are incompatible with the measured values; the stone is quartz (citrine or heat-treated amethyst), RI 1.544, SG 2.65, hardness 7"
isCorrect: true
rationale: |
Each measured property eliminates diamond decisively: RI 1.544 is far below
@@ -22,21 +22,21 @@ options:
While it is true that diamond is isotropic (cubic) and would theoretically give
a single constant shadow edge, diamond's RI of 2.417 places it above the
refractometer's contact-liquid limit (~1.79) [ref:read-gemmology-3e]. Diamond gives NO shadow edge on the
- standard refractometer — the scale appears uniformly bright. The tested stone gives
+ standard refractometer – the scale appears uniformly bright. The tested stone gives
a shadow edge at 1.544, which is unambiguously a stone with RI 1.544, not diamond.
- text: "The vitreous lustre eliminates diamond, which has adamantine lustre; the other properties are consistent with diamond simulants including some glass"
isCorrect: false
rationale: |
- Lustre alone does not eliminate diamond — it is a supporting observation, not a
+ Lustre alone does not eliminate diamond – it is a supporting observation, not a
decisive one, because lustre is affected by surface quality and polish [ref:read-gemmology-3e]. Glass has RI
- typically 1.44–1.70, SG approximately 2.5, and conchoidal fracture — overlapping
+ typically 1.44–1.70, SG approximately 2.5, and conchoidal fracture – overlapping
somewhat with the test results. However, glass is amorphous, not a crystal.
The RI, SG, and hardness all point definitively to quartz rather than glass:
SG 2.65 is specific to quartz, not glass [ref:read-gemmology-3e].
rationaleCorrect: |
Diamond elimination rests on three simultaneous mismatches: (1) RI 1.544 vs diamond
- 2.417 [ref:read-gemmology-3e] — a difference of 0.873, enormous by gemmological standards; (2) SG 2.65 vs
- diamond 3.52 [ref:read-gemmology-3e] — nearly 1.0 unit difference; (3) hardness 7 vs diamond 10 [ref:read-gemmology-3e] — the maximum
+ 2.417 [ref:read-gemmology-3e] – a difference of 0.873, enormous by gemmological standards; (2) SG 2.65 vs
+ diamond 3.52 [ref:read-gemmology-3e] – nearly 1.0 unit difference; (3) hardness 7 vs diamond 10 [ref:read-gemmology-3e] – the maximum
difference on the Mohs scale. Any single one of these would eliminate diamond; all three
together with conchoidal fracture and vitreous lustre confirm quartz. Citrine is the
most common yellow quartz gem; it can be natural (trace iron) or heat-treated amethyst [ref:read-gemmology-3e].
diff --git a/src/content/questions/fundamentals/phys-prop-003.yaml b/src/content/questions/fundamentals/phys-prop-003.yaml
index 44fc853..7c1d441 100644
--- a/src/content/questions/fundamentals/phys-prop-003.yaml
+++ b/src/content/questions/fundamentals/phys-prop-003.yaml
@@ -8,18 +8,18 @@ stem: |
would confirm each?
type: mcq
options:
- - text: "Jadeite SG is 3.25–3.35, while peridot (olivine) SG is 3.28–3.48; the spot RI is the better discriminator — jadeite RI approximately 1.65–1.67, peridot RI 1.654–1.690 — but both overlap so SG plus RI together give highest confidence"
+ - text: "Jadeite SG is 3.25–3.35, while peridot (olivine) SG is 3.28–3.48; the spot RI is the better discriminator – jadeite RI approximately 1.65–1.67, peridot RI 1.654–1.690 – but both overlap so SG plus RI together give highest confidence"
isCorrect: false
rationale: |
This answer correctly notes the overlap in both SG and RI ranges for jadeite and
peridot [ref:read-gemmology-3e], making it a partially correct observation. However, the question asks
for the MOST efficient single measurement to separate them. The key discriminator
- is not one property in isolation but the combination — and the answer underestimates
+ is not one property in isolation but the combination – and the answer underestimates
the value of spectroscopic testing (peridot's characteristic absorption spectrum
with iron bands is highly diagnostic) or the crystal form under the microscope
(jadeite is polycrystalline with interlocking grain texture; peridot is single
crystal with lily-pad inclusions).
- - text: "SG is the most efficient single discriminator for this pair: jadeite peaks at 3.25–3.35 (mean ~3.34), peridot ranges 3.28–3.48 with a typical mean near 3.34 too — they overlap significantly, so the spectroscope showing peridot's iron absorption at 493 nm is the most efficient single definitive test"
+ - text: "SG is the most efficient single discriminator for this pair: jadeite peaks at 3.25–3.35 (mean ~3.34), peridot ranges 3.28–3.48 with a typical mean near 3.34 too – they overlap significantly, so the spectroscope showing peridot's iron absorption at 493 nm is the most efficient single definitive test"
isCorrect: true
rationale: |
Jadeite SG 3.25–3.35 and peridot SG 3.28–3.48 overlap substantially [ref:read-gemmology-3e], and the
@@ -35,16 +35,16 @@ options:
rationale: |
Both jadeite and peridot have virtually identical Mohs hardness ranges (jadeite
6.5–7; peridot 6.5–7) [ref:read-gemmology-3e]. Hardness testing would not separate them and is also a
- damaging test — inappropriate for a finished cabochon submitted by a client.
+ damaging test – inappropriate for a finished cabochon submitted by a client.
Recommending hardness testing on a finished gem is poor laboratory practice when
non-destructive optical and spectroscopic methods are available.
rationaleCorrect: |
The jadeite-versus-peridot discrimination is one of the classic "overlapping SG and RI"
problems in gemmology [ref:read-gemmology-3e]. Both cluster around SG 3.3 and RI 1.65–1.67 in spot readings.
- The decisive non-destructive tests are: (1) spectroscope — peridot shows iron absorption
+ The decisive non-destructive tests are: (1) spectroscope – peridot shows iron absorption
bands (particularly ~493 nm) [ref:read-gemmology-3e]; jadeite shows a different pattern or may be featureless;
- (2) microscopy — peridot is single crystal with characteristic lily-pad chromite inclusions;
- jadeite is polycrystalline with an interlocking "sugary" texture [ref:read-gemmology-3e]; (3) birefringence —
+ (2) microscopy – peridot is single crystal with characteristic lily-pad chromite inclusions;
+ jadeite is polycrystalline with an interlocking "sugary" texture [ref:read-gemmology-3e]; (3) birefringence –
peridot (biaxial positive, birefringence 0.036) will show strong birefringence effects on
the refractometer on a polished facet; jadeite as a polycrystalline aggregate shows no
net birefringence [ref:read-gemmology-3e].
diff --git a/src/content/questions/fundamentals/phys-prop-004.yaml b/src/content/questions/fundamentals/phys-prop-004.yaml
index e30ba97..8b86a9e 100644
--- a/src/content/questions/fundamentals/phys-prop-004.yaml
+++ b/src/content/questions/fundamentals/phys-prop-004.yaml
@@ -7,7 +7,7 @@ stem: |
1.718; Stone B edge is at 1.434. Identify both stones correctly.
type: mcq
options:
- - text: "Stone A: spinel (RI 1.718, SG 3.58–3.61); Stone B: fluorite (RI 1.434, SG 3.18) — the SG values are consistent with these identifications within measurement error for small stones"
+ - text: "Stone A: spinel (RI 1.718, SG 3.58–3.61); Stone B: fluorite (RI 1.434, SG 3.18) – the SG values are consistent with these identifications within measurement error for small stones"
isCorrect: true
rationale: |
Stone A: RI 1.718 matches spinel (cubic, isotropic, SG typically 3.58–3.61) [ref:read-gemmology-3e].
@@ -17,18 +17,18 @@ options:
Stone B: RI 1.434 matches fluorite (cubic, isotropic, SG 3.18) [ref:read-gemmology-3e]. The measured 3.15
is close to the expected 3.18, within the ±0.01–0.02 precision of a careful
hydrostatic measurement on a small stone.
- - text: "Stone A: glass (RI 1.718, SG 3.42); Stone B: quartz (RI 1.434, SG 3.15) — both are low-value simulants"
+ - text: "Stone A: glass (RI 1.718, SG 3.42); Stone B: quartz (RI 1.434, SG 3.15) – both are low-value simulants"
isCorrect: false
rationale: |
Glass can achieve RI 1.718 by adding heavy-metal oxides, but glass SG at that RI
would be approximately 4.5–5.0 (high-lead glass), not 3.42 [ref:read-gemmology-3e]. Additionally, quartz
- has RI 1.544–1.553, not 1.434 [ref:read-gemmology-3e] — Stone B's RI of 1.434 is far below any quartz value.
- - text: "Stone A: grossular garnet (RI ~1.73–1.76, SG ~3.58); Stone B: apatite (RI ~1.63, SG ~3.20) — both close matches by SG"
+ has RI 1.544–1.553, not 1.434 [ref:read-gemmology-3e] – Stone B's RI of 1.434 is far below any quartz value.
+ - text: "Stone A: grossular garnet (RI ~1.73–1.76, SG ~3.58); Stone B: apatite (RI ~1.63, SG ~3.20) – both close matches by SG"
isCorrect: false
rationale: |
Grossular garnet RI ranges approximately 1.73–1.76 [ref:read-gemmology-3e], which is well above the
measured shadow edge at 1.718. Apatite RI is approximately 1.630–1.640 with
- birefringence 0.002–0.006 — far above the measured 1.434 [ref:read-gemmology-3e]. In gemmological
+ birefringence 0.002–0.006 – far above the measured 1.434 [ref:read-gemmology-3e]. In gemmological
identification, RI is typically the most precise instrument measurement; mismatches
of 0.02 or more in RI are decisive.
rationaleCorrect: |
diff --git a/src/content/questions/fundamentals/phys-prop-005.yaml b/src/content/questions/fundamentals/phys-prop-005.yaml
index 36fbe13..f9c06c4 100644
--- a/src/content/questions/fundamentals/phys-prop-005.yaml
+++ b/src/content/questions/fundamentals/phys-prop-005.yaml
@@ -1,9 +1,9 @@
id: phys-prop-005
stem: |
A gemmologist is presented with three orange stones of similar colour and cut. Physical
- testing reveals: Stone 1 — RI 1.620–1.640, SG 3.06, uniaxial negative, strong
- pleochroism (orange and yellow); Stone 2 — RI 1.654–1.690, SG 3.34, biaxial positive,
- weak pleochroism; Stone 3 — single constant edge RI approximately 1.810 (above normal
+ testing reveals: Stone 1 – RI 1.620–1.640, SG 3.06, uniaxial negative, strong
+ pleochroism (orange and yellow); Stone 2 – RI 1.654–1.690, SG 3.34, biaxial positive,
+ weak pleochroism; Stone 3 – single constant edge RI approximately 1.810 (above normal
refractometer range, reading estimated from edge position), SG 3.84, isotropic.
Identify all three correctly.
type: mcq
@@ -12,7 +12,7 @@ options:
isCorrect: true
rationale: |
Stone 1 matches orange tourmaline: trigonal, uniaxial negative, RI 1.620–1.640,
- SG 3.06, strong dichroism [ref:read-gemmology-3e] — tourmaline shows the strongest pleochroism of any
+ SG 3.06, strong dichroism [ref:read-gemmology-3e] – tourmaline shows the strongest pleochroism of any
common gem. Stone 2 matches peridot: orthorhombic, biaxial positive, RI 1.654–1.690,
SG 3.28–3.48, weak pleochroism [ref:read-gemmology-3e]. Stone 3 matches spessartine garnet: cubic (isotropic),
RI approximately 1.800–1.820 (above standard refractometer range), SG 3.8–4.25 [ref:read-gemmology-3e].
@@ -22,13 +22,13 @@ options:
isCorrect: false
rationale: |
Sapphire (corundum) is trigonal and uniaxial negative, which matches Stone 1's
- optic character. However, sapphire RI is 1.762–1.770 and SG is 3.99–4.01 [ref:read-gemmology-3e] — both
+ optic character. However, sapphire RI is 1.762–1.770 and SG is 3.99–4.01 [ref:read-gemmology-3e] – both
significantly higher than the measured 1.620–1.640 and 3.06. The RI of 1.620–1.640
is far below corundum's range and is instead consistent with tourmaline [ref:read-gemmology-3e].
- text: "Stone 1: orange tourmaline; Stone 2: citrine; Stone 3: hessonite grossular garnet"
isCorrect: false
rationale: |
- Citrine (yellow quartz) is trigonal, uniaxial positive, RI 1.544–1.553, SG 2.65 [ref:read-gemmology-3e] —
+ Citrine (yellow quartz) is trigonal, uniaxial positive, RI 1.544–1.553, SG 2.65 [ref:read-gemmology-3e] –
none of which match Stone 2's biaxial positive character, RI 1.654–1.690, or SG 3.34.
Stone 3's RI near 1.810 is too high for hessonite grossular garnet (RI typically
1.73–1.76, SG 3.57–3.73) [ref:read-gemmology-3e]. An RI of 1.81 points to spessartine (Mn-Al garnet, RI
@@ -36,7 +36,7 @@ options:
rationaleCorrect: |
Three orange gems with overlapping colour but distinct properties: (1) Orange tourmaline
(elbaite): uniaxial negative, RI 1.620–1.640, SG 3.06, strong dichroism [ref:read-gemmology-3e]; (2) Peridot
- (olivine): biaxial positive, RI 1.654–1.690, SG 3.28–3.48, weak pleochroism —
+ (olivine): biaxial positive, RI 1.654–1.690, SG 3.28–3.48, weak pleochroism –
distinctive high birefringence (0.036) makes doubling visible [ref:read-gemmology-3e]; (3) Spessartine garnet:
cubic/isotropic, RI 1.80–1.82 (above refractometer), SG 3.8–4.25, no pleochroism [ref:read-gemmology-3e].
The three-way differentiation relies on optic character first (isotropic/uniaxial/
diff --git a/src/content/questions/fundamentals/phys-prop-006.yaml b/src/content/questions/fundamentals/phys-prop-006.yaml
index 0279385..cdb528c 100644
--- a/src/content/questions/fundamentals/phys-prop-006.yaml
+++ b/src/content/questions/fundamentals/phys-prop-006.yaml
@@ -7,7 +7,7 @@ stem: |
"blue spinel." Evaluate this identification for each stone separately.
type: mcq
options:
- - text: "Stone A is correctly identified as blue spinel (RI 1.712–1.720, SG 3.58–3.61, isotropic); Stone B is misidentified — the SG 4.00, RI ~1.77, and birefringence confirm blue sapphire (corundum), not spinel"
+ - text: "Stone A is correctly identified as blue spinel (RI 1.712–1.720, SG 3.58–3.61, isotropic); Stone B is misidentified – the SG 4.00, RI ~1.77, and birefringence confirm blue sapphire (corundum), not spinel"
isCorrect: true
rationale: |
Stone A matches spinel precisely: cubic (isotropic), RI 1.712–1.720, SG 3.58–3.61 [ref:read-gemmology-3e].
@@ -16,17 +16,17 @@ options:
SG 4.00 is the definitive value for corundum (SG 3.99–4.01) [ref:read-gemmology-3e], far above spinel's
3.58–3.61; visible birefringence under a loupe confirms double refraction, ruling
out isotropic spinel; RI ~1.77 matches corundum (1.762–1.770) [ref:read-gemmology-3e].
- - text: "Both stones are blue spinel — SG and RI variations are within the normal range for spinel from different localities"
+ - text: "Both stones are blue spinel – SG and RI variations are within the normal range for spinel from different localities"
isCorrect: false
rationale: |
- Spinel SG does not range up to 4.00 from locality variation alone — the
+ Spinel SG does not range up to 4.00 from locality variation alone – the
compositional range (Mg replaced by Fe, Zn, Mn) does slightly shift SG, but
the maximum for gem spinel is approximately 3.63–3.72 for iron-bearing varieties,
not 4.00 [ref:read-gemmology-3e]. A difference of 0.40 SG units cannot be explained by locality variation;
4.00 is a diagnostic, species-level value for corundum, not spinel [ref:read-gemmology-3e]. Additionally,
visible birefringence (double image) under a loupe in Stone B rules out any cubic
mineral including spinel.
- - text: "Stone A is blue topaz (RI ~1.62, SG ~3.50); Stone B is blue sapphire — blue topaz can appear similar to spinel but is biaxial"
+ - text: "Stone A is blue topaz (RI ~1.62, SG ~3.50); Stone B is blue sapphire – blue topaz can appear similar to spinel but is biaxial"
isCorrect: false
rationale: |
Blue topaz RI is 1.619–1.627, clearly below the spot reading of approximately
@@ -34,11 +34,11 @@ options:
Blue topaz is also biaxial (orthorhombic) and would show birefringence on a
polariscope, not isotropic behaviour [ref:read-gemmology-3e].
rationaleCorrect: |
- Stone A: spinel (RI 1.718, SG 3.60, isotropic) — all three properties within published
+ Stone A: spinel (RI 1.718, SG 3.60, isotropic) – all three properties within published
spinel range [ref:read-gemmology-3e]. Stone B: blue sapphire (corundum, RI 1.762–1.770, SG 4.00, uniaxial
- negative with visible birefringence) — the SG of 4.00 is one of the most precise and
+ negative with visible birefringence) – the SG of 4.00 is one of the most precise and
diagnostic values in gemmology (corundum SG 3.99–4.01) [ref:read-gemmology-3e]. Blue sapphire and blue spinel
- are the classic pair historically confused before the advent of gemmological instruments —
+ are the classic pair historically confused before the advent of gemmological instruments –
the Black Prince's Ruby and Timur Ruby in the English crown jewels are actually red
spinels mistaken for rubies for centuries.
difficulty: 3
diff --git a/src/content/questions/fundamentals/phys-prop-007.yaml b/src/content/questions/fundamentals/phys-prop-007.yaml
index 8ca0b59..5d03f84 100644
--- a/src/content/questions/fundamentals/phys-prop-007.yaml
+++ b/src/content/questions/fundamentals/phys-prop-007.yaml
@@ -28,12 +28,12 @@ options:
- text: "Both stones are green sapphire (corundum); the RI range 1.577–1.583 represents omega only, while 1.620–1.640 represents different cut orientations of corundum"
isCorrect: false
rationale: |
- Corundum RI is 1.762–1.770 [ref:read-gemmology-3e] — neither 1.577–1.583 nor 1.620–1.640 is within
+ Corundum RI is 1.762–1.770 [ref:read-gemmology-3e] – neither 1.577–1.583 nor 1.620–1.640 is within
corundum's published range by a large margin (0.18+ units difference). No
orientation of corundum can give an RI reading of 1.577 on a standard refractometer;
the minimum omega for corundum is 1.762.
rationaleCorrect: |
- Green beryl (emerald) and green tourmaline are both uniaxial negative — a property
+ Green beryl (emerald) and green tourmaline are both uniaxial negative – a property
they share [ref:read-gemmology-3e]. The discrimination rests entirely on RI range and SG: emerald RI 1.577–1.583,
SG 2.67–2.78; tourmaline RI 1.620–1.640, SG 3.06 [ref:read-gemmology-3e]. The ~0.04 RI gap between maximum
emerald (1.583) and minimum tourmaline (1.620) is large enough to be read clearly on
diff --git a/src/content/questions/fundamentals/phys-prop-008.yaml b/src/content/questions/fundamentals/phys-prop-008.yaml
index c5a82f4..b788c01 100644
--- a/src/content/questions/fundamentals/phys-prop-008.yaml
+++ b/src/content/questions/fundamentals/phys-prop-008.yaml
@@ -2,7 +2,7 @@ id: phys-prop-008
stem: |
A kyanite crystal is being assessed for cutting. A student measures the hardness
in two directions: parallel to the length of the crystal (along the c-axis) and
- perpendicular to the length. The readings are markedly different — approximately
+ perpendicular to the length. The readings are markedly different – approximately
4.5–5 parallel to the c-axis and 6.5–7 perpendicular. The student asks why the
hardness differs so dramatically in a single mineral species. What is the correct
mineralogical explanation?
@@ -17,7 +17,7 @@ options:
produces weaker planes parallel to the length (c-axis direction), giving hardness
4.5–5 in that direction, and stronger planes perpendicular, giving 6.5–7 [ref:read-gemmology-3e].
This property gave kyanite its historical name "disthene" (two strengths). The
- same mineral — same crystal, same composition — scratches easily along one
+ same mineral – same crystal, same composition – scratches easily along one
direction and resists scratching in another.
- text: "The two measurements were taken on different zones of the crystal that have different compositions due to chemical zoning, causing the hardness variation"
isCorrect: false
@@ -43,8 +43,8 @@ rationaleCorrect: |
it can vary by 2 full Mohs units depending on the direction of the test [ref:read-gemmology-3e]. This has
significant practical implications: cutting and polishing kyanite is challenging because
the polishing wheel must be oriented correctly for each facet. Directional hardness is
- not unique to kyanite — diamond also varies by direction (hardest along octahedral,
- softest across dodecahedral) [ref:read-gemmology-3e] — but kyanite is the most extreme and pedagogically
+ not unique to kyanite – diamond also varies by direction (hardest along octahedral,
+ softest across dodecahedral) [ref:read-gemmology-3e] – but kyanite is the most extreme and pedagogically
useful example in gemmology.
difficulty: 2
category: fundamentals
diff --git a/src/content/questions/fundamentals/phys-prop-009.yaml b/src/content/questions/fundamentals/phys-prop-009.yaml
index 8ce36c1..6a93fec 100644
--- a/src/content/questions/fundamentals/phys-prop-009.yaml
+++ b/src/content/questions/fundamentals/phys-prop-009.yaml
@@ -18,7 +18,7 @@ options:
distinguish them on the refractometer with reasonable care, making the spot RI
the most practical single test [ref:read-gemmology-3e]. SG also separates them (nephrite 2.95–3.10 vs
jadeite 3.25–3.35) but requires hydrostatic weighing equipment.
- - text: "Stone A is jadeite; Stone B is nephrite — the RI values for jade types are frequently confused"
+ - text: "Stone A is jadeite; Stone B is nephrite – the RI values for jade types are frequently confused"
isCorrect: false
rationale: |
The assignment is reversed. Jadeite has the higher RI (~1.65 spot) because of its
@@ -34,16 +34,16 @@ options:
Nephrite's fibrous, interlocking amphibole structure gives it exceptional toughness
but does not prevent a polished surface suitable for gemmological testing.
The spot reading technique is specifically designed for curved and flat polished
- surfaces that are not faceted — it works well on both jade types [ref:read-gemmology-3e].
+ surfaces that are not faceted – it works well on both jade types [ref:read-gemmology-3e].
rationaleCorrect: |
- Nephrite and jadeite are both "jade" but are entirely different minerals — nephrite is
+ Nephrite and jadeite are both "jade" but are entirely different minerals – nephrite is
an amphibole aggregate (tremolite-actinolite), jadeite is a pyroxene single mineral [ref:read-gemmology-3e].
Their separation is one of the most practically important distinctions in gem trade,
as top-quality "Imperial" jadeite (translucent vivid green, Myanmar) commands prices
far exceeding nephrite. The spot RI is the most immediately accessible test: nephrite
~1.60–1.63, jadeite ~1.65–1.68 [ref:read-gemmology-3e]. SG confirms: nephrite 2.95–3.10, jadeite 3.25–3.35 [ref:read-gemmology-3e].
Both show polycrystalline texture under the microscope; spectroscopy (jadeite
- absorption at 437 nm — always present, even in non-green jadeite) provides additional
+ absorption at 437 nm – always present, even in non-green jadeite) provides additional
confirmation [ref:read-gemmology-3e]. Never identify jade by colour alone: dyed quartzite and glass can
mimic green colour convincingly.
difficulty: 3
diff --git a/src/content/questions/fundamentals/phys-prop-010.yaml b/src/content/questions/fundamentals/phys-prop-010.yaml
index 764a14c..f2e96fb 100644
--- a/src/content/questions/fundamentals/phys-prop-010.yaml
+++ b/src/content/questions/fundamentals/phys-prop-010.yaml
@@ -11,8 +11,8 @@ options:
- text: "Moonstone (orthoclase feldspar), adularescence from light scattering between albite lamellae; the optical phenomenon eliminates white chalcedony and milky quartz, which show no adularescence"
isCorrect: true
rationale: |
- Adularescence — the floating blue-white sheen caused by light scattering between
- alternating layers of orthoclase and albite — is virtually diagnostic for moonstone
+ Adularescence – the floating blue-white sheen caused by light scattering between
+ alternating layers of orthoclase and albite – is virtually diagnostic for moonstone
(adularia/orthoclase feldspar) [ref:read-gemmology-3e]. The SG of 3.02 is above the normal orthoclase
range of 2.56–2.59, suggesting this might be a high-SG variety or include a
measurement error; however, the spot RI ~1.53 (orthoclase RI ~1.52–1.54) [ref:read-gemmology-3e] and
@@ -23,7 +23,7 @@ options:
rationale: |
Peristerite is an albite-rich plagioclase that can show adularescence (sometimes
called "rainbow moonstone" in the trade, though this is a misnomer) [ref:read-gemmology-3e]. Peristerite
- SG is typically 2.62–2.65 and RI approximately 1.53–1.55 — overlapping partially
+ SG is typically 2.62–2.65 and RI approximately 1.53–1.55 – overlapping partially
with orthoclase. The measured SG of 3.02 is too high for peristerite; distinguishing
peristerite from orthoclase moonstone requires precise RI measurement and spectroscopy,
not the spot method.
@@ -38,15 +38,15 @@ options:
change with angle. Labradorite SG 2.69–2.72 and RI 1.56–1.57 [ref:read-gemmology-3e] are also clearly
different from the measured values.
rationaleCorrect: |
- Moonstone (adularia/orthoclase feldspar) is identified by its adularescence — a
+ Moonstone (adularia/orthoclase feldspar) is identified by its adularescence – a
floating blue-white sheen caused by Rayleigh scattering from submicroscopic albite
lamellae exsolved within the orthoclase host [ref:read-gemmology-3e]. This optical effect is specific to
moonstone among common gem feldspars and distinguishes it from quartz-group stones
- (which do not show adularescence) and labradorite (which shows labradorescence —
+ (which do not show adularescence) and labradorite (which shows labradorescence –
spectral colour play, visually distinct) [ref:read-gemmology-3e]. SG ~2.56–2.59 for pure orthoclase; RI
1.518–1.526 (alpha) to 1.524–1.533 (gamma), mean ~1.52–1.53 [ref:read-gemmology-3e]. The spot reading of
~1.53 is consistent. Note: "rainbow moonstone" in the trade is often labradorite,
- not orthoclase moonstone — the trade name is misleading [ref:read-gemmology-3e].
+ not orthoclase moonstone – the trade name is misleading [ref:read-gemmology-3e].
difficulty: 3
category: fundamentals
conceptTags:
diff --git a/src/content/questions/identification/inclusion-fingerprint-001.yaml b/src/content/questions/identification/inclusion-fingerprint-001.yaml
index 81a5ae9..5a27721 100644
--- a/src/content/questions/identification/inclusion-fingerprint-001.yaml
+++ b/src/content/questions/identification/inclusion-fingerprint-001.yaml
@@ -9,15 +9,15 @@ stem: |
cloud-like appearance. What do these two different fingerprint appearances indicate?
type: mcq
options:
- - text: "Stone 1 (sharp, well-defined network) has a natural fingerprint from a healed fracture; Stone 2 (fuzzy, cotton-like pattern) shows flux fingerprints — the different texture indicates heat treatment in the presence of flux material"
+ - text: "Stone 1 (sharp, well-defined network) has a natural fingerprint from a healed fracture; Stone 2 (fuzzy, cotton-like pattern) shows flux fingerprints – the different texture indicates heat treatment in the presence of flux material"
isCorrect: true
rationale: |
Natural fingerprint inclusions form when a fracture heals around residual fluid,
trapping droplets in a regular lace-like pattern [ref:gubelin-koivula-vol1]. The healing process in natural
conditions (geological time, groundwater or metamorphic fluid) produces sharp,
well-defined droplet edges because the healing is complete and the fluid droplets
- are clearly bounded. Flux fingerprints — formed when fractures are healed during
- high-temperature treatment in the presence of a flux (e.g. borax) — show a
+ are clearly bounded. Flux fingerprints – formed when fractures are healed during
+ high-temperature treatment in the presence of a flux (e.g. borax) – show a
distinctly different texture: fuzzy, cottony, or cloud-like edges because the
molten flux material partially fills the fracture and leaves an irregular,
glassy residue with less well-defined droplet boundaries [ref:gubelin-koivula-vol1].
@@ -25,11 +25,11 @@ options:
isCorrect: false
rationale: |
Curved growth striae in Verneuil synthetic corundum are fine curved lines that
- extend across the stone parallel to the growth front — they do not form lace-like
+ extend across the stone parallel to the growth front – they do not form lace-like
droplet networks resembling fingerprints [ref:gubelin-koivula-vol1]. Fingerprint inclusions in both natural
and flux-treated corundums form from healed fractures containing fluid; their
origin is mechanical (a fracture that healed), not from the initial growth process [ref:read-gemmology-3e].
- Stone 2's fuzzy appearance is not from a "partially healed fissure" — a partially
+ Stone 2's fuzzy appearance is not from a "partially healed fissure" – a partially
healed fracture would show clear fluid or open fracture areas, not a cottony
texture throughout the fingerprint.
- text: "Both fingerprints are identical in nature; the apparent texture difference is an artefact of different illumination angles during observation and has no diagnostic significance"
@@ -37,7 +37,7 @@ options:
rationale: |
The textural difference between natural fingerprints (sharp, well-defined droplets)
and flux fingerprints (fuzzy, cottony) is a genuine physical difference in the
- nature of the included material — not an illumination artefact [ref:gubelin-koivula-vol1]. This distinction
+ nature of the included material – not an illumination artefact [ref:gubelin-koivula-vol1]. This distinction
is documented in the gemmological literature as a treatment indicator. Experienced
gemmologists deliberately use both darkfield and fibre-optic illumination to
confirm the textures are stable across lighting conditions.
@@ -49,7 +49,7 @@ rationaleCorrect: |
borax or other fluxes; the flux melt partially fills the fracture, producing an
irregular glassy residue with fuzzy boundaries [ref:gubelin-koivula-vol1]. The difference is reproducible
across lighting conditions and magnifications. A laboratory report noting "flux
- fingerprints observed" means heat treatment with a flux material is indicated —
+ fingerprints observed" means heat treatment with a flux material is indicated –
this affects disclosure requirements in the trade [ref:read-gemmology-3e].
difficulty: 4
category: identification
diff --git a/src/content/questions/identification/inclusion-fissure-001.yaml b/src/content/questions/identification/inclusion-fissure-001.yaml
index bcf2128..73d4c73 100644
--- a/src/content/questions/identification/inclusion-fissure-001.yaml
+++ b/src/content/questions/identification/inclusion-fissure-001.yaml
@@ -10,21 +10,21 @@ options:
- text: "A healed fingerprint shows a regular network of tiny fluid droplets and remains internal with no light leakage from the surface; a fissure shows continuity to the surface (visible as a bright line under reflected light) and often shows iridescence from thin-film interference or allows contact liquid to enter the fracture during refractometer testing"
isCorrect: true
rationale: |
- The key discriminators are: (1) internal vs. surface-reaching — a fingerprint is
+ The key discriminators are: (1) internal vs. surface-reaching – a fingerprint is
fully enclosed within the gem [ref:gubelin-koivula-vol1]; under fibre-optic or reflected light, a fissure
- shows bright light leakage where it reaches the surface; (2) iridescence — open
+ shows bright light leakage where it reaches the surface; (2) iridescence – open
or partially open fissures show interference colours (iridescence) from a thin
air gap within the fracture; healed fingerprints have no air gap and show no
- iridescence [ref:gubelin-koivula-vol1]; (3) contact liquid test — when testing on the refractometer, contact
+ iridescence [ref:gubelin-koivula-vol1]; (3) contact liquid test – when testing on the refractometer, contact
liquid can enter a surface-reaching fissure and may affect the reading [ref:anderson-gem-testing];
- (4) the network pattern — a true fingerprint shows the characteristic lace-like
+ (4) the network pattern – a true fingerprint shows the characteristic lace-like
droplet pattern [ref:gubelin-koivula-vol1]. The distinction matters for appraisal: a surface-reaching fissure
reduces durability and value; an internal fingerprint is less concerning [ref:read-gemmology-3e].
- text: "Rotate the stone under crossed polars; a fingerprint shows birefringence effects, while a fissure does not"
isCorrect: false
rationale: |
Neither a fingerprint inclusion nor a fissure shows intrinsic birefringence effects
- between crossed polars — these are not inherently birefringent features [ref:read-gemmology-3e]. The host
+ between crossed polars – these are not inherently birefringent features [ref:read-gemmology-3e]. The host
gem's birefringence is what is observed on the polariscope, not the inclusion type.
A birefringent host (e.g. sapphire) shows birefringence across the whole stone,
regardless of whether it contains fingerprints or fissures. Using the polariscope
@@ -43,7 +43,7 @@ options:
rationaleCorrect: |
The fingerprint/fissure distinction is fundamental to gem appraisal because the two
features have very different implications for durability and value [ref:read-gemmology-3e]. A fully internal
- fingerprint does not reach the surface — it cannot be a point of entry for cleaning
+ fingerprint does not reach the surface – it cannot be a point of entry for cleaning
solutions, setting prongs, or mechanical stress propagation. A surface-reaching fissure
is a vulnerability: it can extend with use, trap foreign material, and reduce the gem's
useful life in jewellery. The practical tests are: (1) low-power reflected light scanning
diff --git a/src/content/questions/identification/inclusion-growth-tube-001.yaml b/src/content/questions/identification/inclusion-growth-tube-001.yaml
index a6c5123..7778ac2 100644
--- a/src/content/questions/identification/inclusion-growth-tube-001.yaml
+++ b/src/content/questions/identification/inclusion-growth-tube-001.yaml
@@ -8,13 +8,13 @@ stem: |
identification of these features, and why does their presence support natural origin?
type: mcq
options:
- - text: "Growth tubes, not rutile silk; growth tubes in tourmaline are hollow or fluid-filled channels parallel to the c-axis, formed during crystal growth — not exsolved needles; their consistent orientation and natural formation process support natural rather than synthetic origin"
+ - text: "Growth tubes, not rutile silk; growth tubes in tourmaline are hollow or fluid-filled channels parallel to the c-axis, formed during crystal growth – not exsolved needles; their consistent orientation and natural formation process support natural rather than synthetic origin"
isCorrect: true
rationale: |
Growth tubes are a characteristic natural inclusion type in tourmaline, formed
parallel to the c-axis during crystal growth as the growing face traps channels
of surrounding fluid or grows around fine particles [ref:gubelin-koivula-vol3]. They are not rutile TiO2
- needles — they are structural growth features. Rutile silk is specific to corundum
+ needles – they are structural growth features. Rutile silk is specific to corundum
(and some garnets) and exsolves from the host lattice as the crystal cools;
it does not occur in tourmaline [ref:read-gemmology-3e]. The two are easily distinguished: silk needles
in corundum are solid TiO2, oriented at 60° intersections; tourmaline growth tubes
@@ -26,24 +26,24 @@ options:
extent in some garnets (almandine) [ref:read-gemmology-3e]. It does not occur in tourmaline via the same
exsolution mechanism. Tourmaline's boron-silicate lattice chemistry does not
support titanium exsolution as rutile in the way corundum's aluminium oxide
- lattice does [ref:read-gemmology-3e]. What the student calls "rutile silk" in tourmaline are growth tubes —
+ lattice does [ref:read-gemmology-3e]. What the student calls "rutile silk" in tourmaline are growth tubes –
physically distinct features (hollow or fluid-filled, parallel to c-axis, formed
during growth, not on cooling) [ref:gubelin-koivula-vol3].
- text: "Cleavage traces; tourmaline has perfect prismatic cleavage parallel to c, producing the parallel lines observed"
isCorrect: false
rationale: |
- Tourmaline has poor to indistinct prismatic cleavage — not perfect cleavage [ref:read-gemmology-3e].
+ Tourmaline has poor to indistinct prismatic cleavage – not perfect cleavage [ref:read-gemmology-3e].
What cleavage exists is rarely expressed as clean, regular parallel lines inside
a polished gem. More importantly, cleavage traces would appear as flat, planar
reflective surfaces cutting through the stone, not as fine channels containing
fluid with visible mobile bubbles. The presence of a mobile bubble within the
- feature is definitive evidence of a fluid-filled channel — a growth tube —
+ feature is definitive evidence of a fluid-filled channel – a growth tube –
not a cleavage trace [ref:gubelin-koivula-vol3].
rationaleCorrect: |
Growth tubes are one of the most characteristic and commonly observed inclusions in
tourmaline [ref:gubelin-koivula-vol3]. They form during crystal growth when the advancing crystal face traps
channels of surrounding fluid or mineral particles. In finished gems, growth tubes
- appear as fine parallel channels along the c-axis — some hollow and reflecting light,
+ appear as fine parallel channels along the c-axis – some hollow and reflecting light,
others filled with residual fluid containing a mobile gas bubble (making them two-phase
inclusions within a growth tube) [ref:gubelin-koivula-vol3]. Their presence confirms natural origin: synthetic
tourmaline is essentially non-existent commercially (tourmaline synthesis is technically
diff --git a/src/content/questions/identification/inclusion-horsetail-001.yaml b/src/content/questions/identification/inclusion-horsetail-001.yaml
index 261fa79..8d8b5ce 100644
--- a/src/content/questions/identification/inclusion-horsetail-001.yaml
+++ b/src/content/questions/identification/inclusion-horsetail-001.yaml
@@ -17,7 +17,7 @@ options:
amphibole) radiating from a central chromite (FeCr2O4) crystal [ref:gubelin-koivula-vol1]. This combination
is virtually diagnostic for demantoid garnet from the Ural Mountain deposits in
Russia [ref:gubelin-koivula-vol1]. The SG of 3.84 is critical because demantoid (andradite, Ca3Fe2(SiO4)3)
- has RI approximately 1.888, above the standard refractometer range [ref:read-gemmology-3e] — no shadow
+ has RI approximately 1.888, above the standard refractometer range [ref:read-gemmology-3e] – no shadow
edge is visible. SG distinguishes demantoid (3.82–3.85) from tsavorite (3.57–3.73),
green tourmaline (3.06), and emerald (2.67–2.78) [ref:read-gemmology-3e].
- text: "Tsavorite garnet (grossular); tsavorite shows fibrous actinolite inclusions in cluster form as a result of its metamorphic origin in Kenya"
@@ -25,10 +25,10 @@ options:
rationale: |
Tsavorite (green grossular garnet) does not show horsetail inclusions. Tsavorite
from Kenya forms in metasomatic calc-silicate rocks and contains typical inclusions
- such as apatite, graphite, and diopside — not fibrous actinolite halos from chromite [ref:gubelin-koivula-vol1].
+ such as apatite, graphite, and diopside – not fibrous actinolite halos from chromite [ref:gubelin-koivula-vol1].
The horsetail inclusion is specific to demantoid from the Ural deposits (and
occasionally other andradite localities) [ref:gubelin-koivula-vol1]. Additionally, tsavorite RI is
- approximately 1.740–1.760, within the standard refractometer range [ref:read-gemmology-3e] — it would give
+ approximately 1.740–1.760, within the standard refractometer range [ref:read-gemmology-3e] – it would give
a visible shadow edge, contradicting the "no shadow edge" observation.
- text: "Chrome tourmaline; chrome tourmaline contains fibrous inclusions radiating from a chromite crystal in characteristic horsetail patterns"
isCorrect: false
@@ -36,11 +36,11 @@ options:
Chrome tourmaline does not show horsetail inclusions. Tourmaline inclusions include
growth tubes parallel to the c-axis, fluid inclusions, and occasionally mineral
crystals, but not the characteristic radial byssolite fibres from a chromite centre
- that define the horsetail [ref:gubelin-koivula-vol3]. Furthermore, chrome tourmaline RI is 1.620–1.640 [ref:read-gemmology-3e] —
+ that define the horsetail [ref:gubelin-koivula-vol3]. Furthermore, chrome tourmaline RI is 1.620–1.640 [ref:read-gemmology-3e] –
it gives a clear shadow edge on the refractometer. The "no shadow edge" observation
eliminates tourmaline before microscopy even begins.
rationaleCorrect: |
- The horsetail inclusion — byssolite fibres radiating from a chromite crystal — is
+ The horsetail inclusion – byssolite fibres radiating from a chromite crystal – is
one of the most celebrated diagnostic features in gemmology and is virtually
pathognomonic for Russian demantoid garnet [ref:gubelin-koivula-vol1]. Demantoid from the Ural Mountains
almost always shows horsetails; demantoid from other localities (Madagascar,
diff --git a/src/content/questions/identification/inclusion-negative-crystal-001.yaml b/src/content/questions/identification/inclusion-negative-crystal-001.yaml
index bc5d3fa..fbcf4fc 100644
--- a/src/content/questions/identification/inclusion-negative-crystal-001.yaml
+++ b/src/content/questions/identification/inclusion-negative-crystal-001.yaml
@@ -2,29 +2,29 @@ id: inclusion-negative-crystal-001
stem: |
A gemmologist examines a blue spinel under the microscope and observes small, regular,
multi-faceted cavities within the stone. Each cavity has the geometric form of a
- regular octahedron — eight triangular faces meeting at precise angles. The cavities
+ regular octahedron – eight triangular faces meeting at precise angles. The cavities
appear either empty (filled with air, showing total internal reflection at their faces)
or partially filled with liquid. A student labels these as "diamond-shaped crystal
inclusions." What is the correct term for these features, and why do they have an
octahedral shape?
type: mcq
options:
- - text: "Negative crystals; the cavities have an octahedral form because spinel (cubic, m3̄m point group) has octahedral habit as its characteristic crystal form — the void takes the shape of the host crystal's symmetry"
+ - text: "Negative crystals; the cavities have an octahedral form because spinel (cubic, m3̄m point group) has octahedral habit as its characteristic crystal form – the void takes the shape of the host crystal's symmetry"
isCorrect: true
rationale: |
Negative crystals are fluid-filled or empty cavities that have the geometric shape
of the host mineral's own crystal form [ref:gubelin-koivula-vol1]. Spinel is cubic (point group m3̄m) and
- crystallises characteristically as octahedra — so cavities that formed by
+ crystallises characteristically as octahedra – so cavities that formed by
dissolution or incomplete crystal growth within spinel take on the octahedral
habit [ref:read-gemmology-3e]. The octahedral shape is an expression of the host crystal's symmetry and
- bond strengths — the surfaces of the cavity form along the {111} crystal faces,
+ bond strengths – the surfaces of the cavity form along the {111} crystal faces,
which represent the low-surface-energy planes of the cubic structure [ref:read-gemmology-3e]. Calling
them "diamond-shaped" is colloquially used by non-specialists but is incorrect
gemmological terminology.
- text: "Fluid inclusions; the octahedral shape indicates the trapped fluid crystallised into an octahedral halite crystal, similar to three-phase inclusions in emerald"
isCorrect: false
rationale: |
- Halite (NaCl) crystallises in the cubic system with a cube habit — cubic (isometric)
+ Halite (NaCl) crystallises in the cubic system with a cube habit – cubic (isometric)
halite forms cubes, not octahedra [ref:read-gemmology-3e]. More importantly, what the student describes
are not solid halite crystals but geometric voids (cavities) with the spinel crystal
form. The distinction between a negative crystal (a void with host-crystal form) and
@@ -37,7 +37,7 @@ options:
Spinel does have imperfect octahedral cleavage on {111}, but cleavage voids would
appear as flat, irregular planar gaps rather than perfect multi-faced enclosed
cavities [ref:read-gemmology-3e]. True octahedral negative crystals are enclosed geometric forms with all
- eight faces meeting cleanly — they are not cleavage features, which are planar and
+ eight faces meeting cleanly – they are not cleavage features, which are planar and
open-ended [ref:gubelin-koivula-vol1].
rationaleCorrect: |
Negative crystals in spinel are one of the classic microscopic features of this species
@@ -45,7 +45,7 @@ rationaleCorrect: |
void shape reflects the host crystal symmetry [ref:gubelin-koivula-vol1]. In spinel (cubic, octahedral habit),
negative crystals take the octahedral form [ref:read-gemmology-3e]. They may be empty (showing total internal
reflection at the {111} faces, giving them a mirror-bright appearance) or partially
- filled with residual fluid. Their presence is a natural origin indicator — synthetic
+ filled with residual fluid. Their presence is a natural origin indicator – synthetic
spinel (flame fusion or hydrothermal) rarely if ever shows perfect natural negative
crystals of this kind [ref:gubelin-koivula-vol1]. The term "negative crystal" is standard in gemmological
and mineralogical literature; students should recognise it and be able to explain
diff --git a/src/content/questions/identification/inclusion-silk-001.yaml b/src/content/questions/identification/inclusion-silk-001.yaml
index 74c90d4..b5a1505 100644
--- a/src/content/questions/identification/inclusion-silk-001.yaml
+++ b/src/content/questions/identification/inclusion-silk-001.yaml
@@ -16,8 +16,8 @@ options:
used in standard ruby enhancement (typically 1200–1800°C), rutile needles begin to
dissolve back into the corundum lattice (TiO2 re-entering the Al2O3 structure) [ref:read-gemmology-3e].
The dissolution starts at the ends and along the length of the needles, producing
- an interrupted or "dotted" appearance [ref:gubelin-koivula-vol1]. This pattern — segments of needle with
- gaps between them — is a well-established indicator of moderate heat treatment [ref:gubelin-koivula-vol1].
+ an interrupted or "dotted" appearance [ref:gubelin-koivula-vol1]. This pattern – segments of needle with
+ gaps between them – is a well-established indicator of moderate heat treatment [ref:gubelin-koivula-vol1].
The seller's claim of "untreated" is contradicted by the dotted silk observation.
- text: "The broken silk needles indicate natural parting of the corundum, which fractures silk as it forms; this is a natural feature not related to treatment"
isCorrect: false
@@ -25,7 +25,7 @@ options:
Natural parting in corundum (along twin planes) occurs at a scale visible as flat
reflective surfaces, not as a breakdown of individual silk needles within the bulk
of the crystal [ref:read-gemmology-3e]. Parting does not selectively interrupt rutile needles mid-length
- while leaving the orientation intact; it would produce a different observation —
+ while leaving the orientation intact; it would produce a different observation –
a flat plane cutting across the stone. The dotted, segmented appearance of silk
needles is specifically associated with thermal dissolution of rutile in the
literature and is not explained by natural parting mechanics [ref:gubelin-koivula-vol1].
@@ -35,7 +35,7 @@ options:
Growth tubes (hollow or fluid-filled channels parallel to the c-axis in some gem
species) are a different inclusion type from rutile silk [ref:gubelin-koivula-vol1]. Rutile silk is solid TiO2
crystallites, not hollow tubes, and they form by exsolution from the corundum lattice
- on cooling — not during primary growth [ref:read-gemmology-3e]. The intersecting pattern at 60° is specific
+ on cooling – not during primary growth [ref:read-gemmology-3e]. The intersecting pattern at 60° is specific
to exsolved rutile silk (the three crystallographic directions of the trigonal corundum
lattice). Growth tubes in tourmaline or aquamarine are parallel to c-axis only and do
not form intersecting networks [ref:gubelin-koivula-vol3].
@@ -46,7 +46,7 @@ rationaleCorrect: |
treatment (partial dissolution) [ref:gubelin-koivula-vol1]; (3) no silk = high-heat treatment (complete dissolution)
or the stone never had silk. The presence of dotted silk is often combined with other
heat-treatment indicators (e.g. healed fissures, altered fingerprints, rutile particles
- re-precipitated on healed surfaces) [ref:gubelin-koivula-vol1]. Reporting "dotted silk observed — heat treatment
+ re-precipitated on healed surfaces) [ref:gubelin-koivula-vol1]. Reporting "dotted silk observed – heat treatment
cannot be excluded" is the correct wording [ref:read-gemmology-3e].
difficulty: 3
category: identification
diff --git a/src/content/questions/identification/inclusion-silk-002.yaml b/src/content/questions/identification/inclusion-silk-002.yaml
index 9db9b7b..5ac3784 100644
--- a/src/content/questions/identification/inclusion-silk-002.yaml
+++ b/src/content/questions/identification/inclusion-silk-002.yaml
@@ -14,7 +14,7 @@ options:
Sri Lankan (Ceylon) corundums typically show longer, more widely spaced, prominent
rutile needles that are easily visible individually under the microscope and often
produce strong asterism in asteriated stones [ref:gubelin-koivula-vol1]. Burmese Mogok corundums show much
- finer, denser, shorter needles — so fine that they scatter light to produce a soft,
+ finer, denser, shorter needles – so fine that they scatter light to produce a soft,
slightly diffused glow called "velvety" or "sleepy" appearance [ref:gubelin-koivula-vol1]. This velvet effect
is associated with the finest Burmese stones and is one of the visual qualities
gemmologists look for in premium rubies and sapphires. The silk characteristics
@@ -23,7 +23,7 @@ options:
isCorrect: false
rationale: |
The origin descriptions are reversed. Mogok Burmese corundums are known for their
- fine, delicate silk — not long, prominent needles [ref:gubelin-koivula-vol1]. Long, clearly separated needles
+ fine, delicate silk – not long, prominent needles [ref:gubelin-koivula-vol1]. Long, clearly separated needles
producing strong asterism are more characteristic of Sri Lankan material. Asterism
in Burmese star rubies does occur, but the silk type that produces the prized
"velvety" quality in non-asteriated Mogok stones is fine and dense [ref:gubelin-koivula-vol1].
@@ -35,7 +35,7 @@ options:
(not classic rutile needles at 60°) that scatter light, producing the famous
velvety or sleepy appearance [ref:gubelin-koivula-vol1]. The term "velvety" is most associated with Kashmir,
but fine Burmese silk can produce a similar soft quality. The question describes
- two stones with classic rutile silk at 60° intersections — this matches Burmese
+ two stones with classic rutile silk at 60° intersections – this matches Burmese
and Sri Lankan origin, not Kashmir. Kashmir sapphire has a different inclusion
suite with specific tourmaline inclusions and zircon halos alongside the fine
particulate scattering [ref:gubelin-koivula-vol1].
diff --git a/src/content/questions/identification/inclusion-three-phase-001.yaml b/src/content/questions/identification/inclusion-three-phase-001.yaml
index 538c301..7267b30 100644
--- a/src/content/questions/identification/inclusion-three-phase-001.yaml
+++ b/src/content/questions/identification/inclusion-three-phase-001.yaml
@@ -9,16 +9,16 @@ stem: |
and what are the three phases described?
type: mcq
options:
- - text: "Colombian emerald; the three-phase inclusion (liquid + mobile gas bubble + solid cuboid crystal — halite, NaCl) is virtually diagnostic of Colombian origin; Zambian emerald shows two-phase inclusions (no solid crystal); synthetic flux-grown emerald shows flux fingerprints and wispy inclusions, not three-phase halite inclusions"
+ - text: "Colombian emerald; the three-phase inclusion (liquid + mobile gas bubble + solid cuboid crystal – halite, NaCl) is virtually diagnostic of Colombian origin; Zambian emerald shows two-phase inclusions (no solid crystal); synthetic flux-grown emerald shows flux fingerprints and wispy inclusions, not three-phase halite inclusions"
isCorrect: true
rationale: |
The three phases are: (1) liquid (saline solution, predominantly NaCl brine);
- (2) gas — a mobile CO2 bubble that moves freely when the stone is tilted;
- (3) solid — a small cuboid (cubic) crystal of halite (NaCl) [ref:gubelin-koivula-vol1]. The cuboid habit
+ (2) gas – a mobile CO2 bubble that moves freely when the stone is tilted;
+ (3) solid – a small cuboid (cubic) crystal of halite (NaCl) [ref:gubelin-koivula-vol1]. The cuboid habit
of the solid crystal is diagnostic: halite crystallises in the cubic system and
- produces perfect cube-shaped crystals [ref:read-gemmology-3e]. This exact combination — irregular jagged
+ produces perfect cube-shaped crystals [ref:read-gemmology-3e]. This exact combination – irregular jagged
cavity (reflecting the host rock environment), saline fluid, CO2 bubble, and
- halite cube — is characteristic of Colombian emerald from the sedimentary-hosted
+ halite cube – is characteristic of Colombian emerald from the sedimentary-hosted
deposits of Muzo, Chivor, and Coscuez [ref:gubelin-koivula-vol1]. Zambian emerald (hosted in schist) shows
a different inclusion suite dominated by two-phase inclusions without halite [ref:gubelin-koivula-vol1].
- text: "Synthetic flux-grown emerald; the three-phase inclusion is characteristic of flux-grown material where the flux solidifies as a cube-shaped crystal inside the void"
@@ -30,7 +30,7 @@ options:
during growth [ref:read-gemmology-3e]. The flux used (typically lithium molybdate or lead oxide-based
fluxes) crystallises as irregular masses or is vitreous (glassy), not as perfect
cubes [ref:read-gemmology-3e]. The cuboid shape of the solid in the described inclusion is characteristic
- of halite, which is geologically formed — not from a synthetic flux medium [ref:gubelin-koivula-vol1]. Synthetic
+ of halite, which is geologically formed – not from a synthetic flux medium [ref:gubelin-koivula-vol1]. Synthetic
emerald inclusions are fundamentally different in appearance from Colombian three-phase
inclusions.
- text: "Zambian emerald; Zambian emeralds commonly show three-phase inclusions with halite cubes from the saline formation environment in Zambia"
@@ -46,13 +46,13 @@ options:
tested in the FGA examination.
rationaleCorrect: |
Three-phase inclusions containing a cuboid halite crystal are virtually diagnostic of
- Colombian emerald origin [ref:gubelin-koivula-vol1] — this is one of the most celebrated and reliably
+ Colombian emerald origin [ref:gubelin-koivula-vol1] – this is one of the most celebrated and reliably
diagnostic features in gemmology. The three phases are: liquid (saline NaCl solution),
gas (CO2 bubble, mobile), and solid (halite cube in cubic habit) [ref:gubelin-koivula-vol1]. The irregular,
jagged cavity walls reflect the surrounding rock fabric. When present, this inclusion type
alone provides compelling evidence for Colombian origin; it is not found in Zambian,
- Brazilian, or synthetic emeralds [ref:gubelin-koivula-vol1]. The Colombian geological setting — where emeralds
- formed in hydrothermal veins cutting through halite-rich black shales — explains the
+ Brazilian, or synthetic emeralds [ref:gubelin-koivula-vol1]. The Colombian geological setting – where emeralds
+ formed in hydrothermal veins cutting through halite-rich black shales – explains the
saline inclusion chemistry [ref:read-gemmology-3e].
difficulty: 3
category: identification
diff --git a/src/content/questions/identification/inclusion-two-phase-001.yaml b/src/content/questions/identification/inclusion-two-phase-001.yaml
index 2f70065..47cde6e 100644
--- a/src/content/questions/identification/inclusion-two-phase-001.yaml
+++ b/src/content/questions/identification/inclusion-two-phase-001.yaml
@@ -7,15 +7,15 @@ stem: |
synthetic origin." A supervisor disagrees. Who is correct, and why?
type: mcq
options:
- - text: "The supervisor is correct; two-phase inclusions (liquid + mobile gas bubble) are natural features found in many gem minerals including topaz, aquamarine, and quartz — they confirm natural origin, not synthetic"
+ - text: "The supervisor is correct; two-phase inclusions (liquid + mobile gas bubble) are natural features found in many gem minerals including topaz, aquamarine, and quartz – they confirm natural origin, not synthetic"
isCorrect: true
rationale: |
Two-phase inclusions (liquid + gas bubble) form when growing crystals trap small
- pockets of surrounding fluid — hydrothermal solutions, metamorphic fluids, or
+ pockets of surrounding fluid – hydrothermal solutions, metamorphic fluids, or
magmatic volatiles [ref:gubelin-koivula-vol1]. The gas bubble forms because the trapped fluid contracts on
cooling, leaving a vapour bubble in equilibrium with the liquid [ref:read-gemmology-3e]. This is a natural
geological process. Synthetic gems produced by flame fusion (Verneuil) contain
- gas bubbles trapped as round or elongated voids — but these are single-phase
+ gas bubbles trapped as round or elongated voids – but these are single-phase
gas inclusions, not liquid + mobile gas [ref:read-gemmology-3e]. Hydrothermal synthetic stones may
contain two-phase inclusions, but the morphology, distribution, and accompanying
features differ from natural stones and require expert discrimination [ref:gubelin-koivula-vol1].
@@ -23,20 +23,20 @@ options:
isCorrect: false
rationale: |
Verneuil flame-fusion synthetic stones contain gas bubbles as single-phase gas
- voids within the solidified melt — they do not contain two-phase liquid + gas
+ voids within the solidified melt – they do not contain two-phase liquid + gas
inclusions [ref:read-gemmology-3e]. The gas voids in Verneuil synthetics are typically round, appear as
bright spheres in darkfield, and show no liquid phase [ref:read-gemmology-3e]. Natural two-phase inclusions
have a distinctly liquid-dominated appearance with a mobile bubble (the bubble is
smaller relative to the liquid volume and moves freely) [ref:gubelin-koivula-vol1]. The presence of liquid is
a key distinguishing feature: liquid is geologically trapped fluid; pure round gas
bubbles are characteristic of melt-origin synthesis [ref:read-gemmology-3e].
- - text: "Neither is correct; two-phase inclusions with mobile bubbles are always diagnostic of fracture filling — a treatment indicator — not natural origin"
+ - text: "Neither is correct; two-phase inclusions with mobile bubbles are always diagnostic of fracture filling – a treatment indicator – not natural origin"
isCorrect: false
rationale: |
Fracture-filling treatments introduce glass or resin into open surface fractures;
the filler may contain gas bubbles trapped in the filler, not mobile liquid +
bubble two-phase inclusions [ref:read-gemmology-3e]. More importantly, the elongated cavities with liquid
- and mobile bubble described here are in the interior of the stone — not along
+ and mobile bubble described here are in the interior of the stone – not along
fractures. Fracture fill is a surface-related treatment and produces a different
microscopic appearance (flow lines in the filler, flattened irregular fracture
planes filled with glass or resin) [ref:read-gemmology-3e]. Natural two-phase inclusions in the interior
@@ -49,9 +49,9 @@ rationaleCorrect: |
Their presence confirms natural trapping of geological fluid and is therefore a natural
origin indicator. The mobility of the gas bubble (visibly moving when the stone is
tilted) confirms that the cavity contains liquid, not just gas [ref:read-gemmology-3e]. Single-phase gas
- bubbles in synthetic Verneuil stones are round, fixed, and contain no liquid — visually
+ bubbles in synthetic Verneuil stones are round, fixed, and contain no liquid – visually
and physically different from natural two-phase inclusions [ref:read-gemmology-3e]. The student's error of
- labelling natural inclusions as synthetic would lead to a false treatment/origin report —
+ labelling natural inclusions as synthetic would lead to a false treatment/origin report –
a serious professional consequence.
difficulty: 3
category: identification
diff --git a/src/content/questions/identification/inclusion-zircon-halo-001.yaml b/src/content/questions/identification/inclusion-zircon-halo-001.yaml
index d70198a..28a97be 100644
--- a/src/content/questions/identification/inclusion-zircon-halo-001.yaml
+++ b/src/content/questions/identification/inclusion-zircon-halo-001.yaml
@@ -21,7 +21,7 @@ options:
1200°C anneals the radiation damage and causes the zircon to re-crystallise and
contract, making the halo fracture close or partially heal [ref:gubelin-koivula-vol1]. Intact, well-developed
zircon halos are therefore an indicator of no or low-temperature treatment [ref:read-gemmology-3e].
- - text: "Lily-pad inclusions; the disc-shaped fractures are chromite crystals in peridot surrounded by stress fractures — a feature of corundum from chromite-bearing environments"
+ - text: "Lily-pad inclusions; the disc-shaped fractures are chromite crystals in peridot surrounded by stress fractures – a feature of corundum from chromite-bearing environments"
isCorrect: false
rationale: |
Lily-pad inclusions are the diagnostic inclusion type of peridot, not corundum [ref:gubelin-koivula-vol1].
@@ -30,14 +30,14 @@ options:
(circular fractures around solid crystals in sapphire) is superficially similar
in geometry but different in identity: the host is corundum (not olivine), and the
included mineral is zircon (not chromite) [ref:read-gemmology-3e]. Lily pads in peridot are not iridescent
- halos — they are flatter, disc-shaped cracks with a different appearance. A student
+ halos – they are flatter, disc-shaped cracks with a different appearance. A student
who remembers "disc-shaped fracture = lily pad" and applies this to sapphire has
made a host-gem error.
- text: "Negative crystals; the iridescent halos are octahedral voids that formed when corundum partially dissolved around trapped fluid during hydrothermal growth"
isCorrect: false
rationale: |
Negative crystals are fluid-filled voids with the geometric shape of the host
- mineral's crystal form — in corundum this would be hexagonal or rhombohedral
+ mineral's crystal form – in corundum this would be hexagonal or rhombohedral
outlines, not circular disc-shaped fracture zones [ref:read-gemmology-3e]. Negative crystals do not
produce the characteristic circular (disc-shaped) fracture halo; they are simply
shaped cavities, typically small and compact [ref:gubelin-koivula-vol1]. The presence of a solid crystal
diff --git a/src/content/questions/species/corundum-vs-spinel-001.yaml b/src/content/questions/species/corundum-vs-spinel-001.yaml
index f624e6b..d652eb0 100644
--- a/src/content/questions/species/corundum-vs-spinel-001.yaml
+++ b/src/content/questions/species/corundum-vs-spinel-001.yaml
@@ -2,7 +2,7 @@ id: corundum-vs-spinel-001
stem: |
A polished red stone gives the following instrument readings in the gemmology
laboratory: RI 1.762–1.770 (two edges touching at 1.762 during rotation), SG 4.00,
- polariscope — lights up at four positions during rotation, LWUV — strong red fluorescence.
+ polariscope – lights up at four positions during rotation, LWUV – strong red fluorescence.
Three candidate identifications are proposed: natural ruby, spinel, or pyrope garnet.
Which candidate is correct and what is the diagnostic reasoning chain?
type: mcq
@@ -11,7 +11,7 @@ options:
isCorrect: true
rationale: |
The polariscope result (lighting at four positions = double refraction) immediately
- eliminates isotropic spinel and isotropic pyrope garnet — both are cubic and remain
+ eliminates isotropic spinel and isotropic pyrope garnet – both are cubic and remain
dark between crossed polars [ref:read-gemmology-3e]. Of the three candidates, only corundum is doubly
refractive (uniaxial negative). RI 1.762–1.770 matches corundum precisely [ref:read-gemmology-3e]; spinel
RI is 1.712–1.720 (too low); pyrope RI is 1.730–1.760 (too low) [ref:read-gemmology-3e]. SG 4.00 matches
@@ -20,28 +20,28 @@ options:
- text: "Spinel; red spinel also shows strong red LWUV fluorescence and RI near 1.718, and fluorescence is the most diagnostic property for red stones"
isCorrect: false
rationale: |
- Red spinel does fluoresce strongly red under LWUV — this is why historical gem
+ Red spinel does fluoresce strongly red under LWUV – this is why historical gem
traders frequently confused spinel with ruby [ref:read-gemmology-3e]. However, fluorescence is explicitly
the LEAST diagnostic property here because both ruby and Burma spinel can show red
LWUV fluorescence. The decisive observations are: (1) the polariscope showing double
- refraction — spinel is isotropic and stays dark [ref:read-gemmology-3e]; (2) RI 1.762–1.770 — spinel RI is
- 1.712–1.720, clearly lower [ref:read-gemmology-3e]; (3) SG 4.00 — spinel SG is 3.58–3.61, clearly lower [ref:read-gemmology-3e].
+ refraction – spinel is isotropic and stays dark [ref:read-gemmology-3e]; (2) RI 1.762–1.770 – spinel RI is
+ 1.712–1.720, clearly lower [ref:read-gemmology-3e]; (3) SG 4.00 – spinel SG is 3.58–3.61, clearly lower [ref:read-gemmology-3e].
- text: "Pyrope garnet; pyrope is deep red and can be confused with ruby; the polariscope result suggests pyrope because garnets often show anomalous double refraction"
isCorrect: false
rationale: |
Anomalous double refraction (ADR) in garnets appears as patchy or mottled light
- patterns between crossed polars — not the clean four-position lighting of true
+ patterns between crossed polars – not the clean four-position lighting of true
double refraction [ref:read-gemmology-3e]. Pyrope is cubic and should appear predominantly dark; ADR is
an irregular strain effect, not systematic double refraction. The stone described
lights up clearly at four positions, which is the behaviour of a genuinely doubly
refractive gem (corundum), not ADR from a garnet [ref:read-gemmology-3e]. Additionally, pyrope RI is
- 1.730–1.760 and SG 3.65–3.87 — both below the measured values [ref:read-gemmology-3e].
+ 1.730–1.760 and SG 3.65–3.87 – both below the measured values [ref:read-gemmology-3e].
rationaleCorrect: |
The ruby/spinel/pyrope discrimination is the most historically important near-miss
- problem in gemmology — the Black Prince's Ruby (Tower of London) is a red spinel [ref:read-gemmology-3e].
+ problem in gemmology – the Black Prince's Ruby (Tower of London) is a red spinel [ref:read-gemmology-3e].
The diagnostic chain is always: optic character first (doubly refractive = not spinel,
not garnet), then RI (1.762–1.770 = corundum range) [ref:read-gemmology-3e], then SG (4.00 = corundum) [ref:read-gemmology-3e].
- Fluorescence confirms but never establishes identification — some Burma spinel also
+ Fluorescence confirms but never establishes identification – some Burma spinel also
fluoresces red [ref:read-gemmology-3e]. A clean four-position lighting on the polariscope is the
single observation that eliminates both cubic candidates simultaneously, before
any measurement is taken. This sequence (polariscope → refractometer → SG) is
diff --git a/src/content/questions/species/corundum-vs-spinel-002.yaml b/src/content/questions/species/corundum-vs-spinel-002.yaml
index 68408af..d691204 100644
--- a/src/content/questions/species/corundum-vs-spinel-002.yaml
+++ b/src/content/questions/species/corundum-vs-spinel-002.yaml
@@ -12,7 +12,7 @@ options:
isCorrect: true
rationale: |
All three measured properties exclude ruby: (1) RI 1.718 is the published value
- for spinel, not corundum (1.762–1.770 — a gap of 0.044 RI units) [ref:read-gemmology-3e]; (2) isotropic
+ for spinel, not corundum (1.762–1.770 – a gap of 0.044 RI units) [ref:read-gemmology-3e]; (2) isotropic
polariscope (stays uniformly dark = no double refraction) rules out corundum, which
is uniaxial negative and lights up between crossed polars [ref:read-gemmology-3e]; (3) SG 3.60 matches
spinel (3.58–3.61) and is far below corundum (3.99–4.01) [ref:read-gemmology-3e]. The red LWUV
@@ -23,7 +23,7 @@ options:
rationale: |
Heat treatment of ruby does not alter its RI or SG to match spinel values. These
are intrinsic properties of the crystal structure (Al2O3 for corundum vs. MgAl2O4
- for spinel) — they cannot be changed by any heat treatment [ref:read-gemmology-3e]. A heat-treated ruby
+ for spinel) – they cannot be changed by any heat treatment [ref:read-gemmology-3e]. A heat-treated ruby
still has RI 1.762–1.770 and SG 3.99–4.01. The measured values (RI 1.718, SG
3.60) cannot be corundum before or after treatment [ref:read-gemmology-3e].
- text: "The stone might be a synthetic ruby; synthetic rubies have lower RI and SG than natural rubies because the flux growth process dilutes the aluminium oxide with flux material"
@@ -32,16 +32,16 @@ options:
Synthetic ruby, whether flame-fusion (Verneuil), flux-grown, or hydrothermal,
has exactly the same chemical composition (Al2O3) and therefore the same RI
(1.762–1.770) and SG (3.99–4.01) as natural ruby [ref:read-gemmology-3e]. The growth process does not
- dilute the corundum lattice — the resulting crystal is pure Al2O3 with the same
+ dilute the corundum lattice – the resulting crystal is pure Al2O3 with the same
physical properties. The measured 1.718 and 3.60 cannot be any form of corundum,
natural or synthetic [ref:read-gemmology-3e].
rationaleCorrect: |
- This is the classic red spinel/ruby confusion — the most commercially important
+ This is the classic red spinel/ruby confusion – the most commercially important
gem misidentification in history. Red spinel (MgAl2O4) and ruby (Al2O3) were
considered the same gem for centuries because both are red and often found together
in alluvial deposits in Myanmar [ref:read-gemmology-3e]. The three-property elimination: (1) RI 1.718 is
spinel [ref:read-gemmology-3e]; (2) isotropic polariscope is spinel (cubic) [ref:read-gemmology-3e]; (3) SG 3.60 is spinel [ref:read-gemmology-3e].
- All three are required — any one alone could theoretically be argued, but all three
+ All three are required – any one alone could theoretically be argued, but all three
together are conclusive. In recent years fine red spinel has achieved prices per carat
approaching those of ruby [ref:read-gemmology-3e].
difficulty: 3
diff --git a/src/content/questions/species/corundum-vs-spinel-003.yaml b/src/content/questions/species/corundum-vs-spinel-003.yaml
index db8c388..32e920e 100644
--- a/src/content/questions/species/corundum-vs-spinel-003.yaml
+++ b/src/content/questions/species/corundum-vs-spinel-003.yaml
@@ -9,21 +9,21 @@ stem: |
and what is the most likely identity here?
type: mcq
options:
- - text: "Natural ruby; silk (rutile needles at 60°) and negative crystals are characteristic natural inclusions — synthetic ruby shows curved growth striae (Verneuil) or flux fingerprints (flux-grown), neither of which matches the described features"
+ - text: "Natural ruby; silk (rutile needles at 60°) and negative crystals are characteristic natural inclusions – synthetic ruby shows curved growth striae (Verneuil) or flux fingerprints (flux-grown), neither of which matches the described features"
isCorrect: true
rationale: |
Rutile silk (TiO2 needles at 60° intersections) is an exsolution feature formed
- during slow natural cooling of corundum — the rutile exsolves from the corundum
+ during slow natural cooling of corundum – the rutile exsolves from the corundum
lattice as the crystal cools [ref:read-gemmology-3e]. This process cannot occur in the rapid Verneuil
(flame fusion) synthesis, which produces a boule in hours. Flux-grown synthetic
ruby shows flux fingerprints (curved or irregular growth planes with flux residue)
and wispy flux inclusions, not straight intersecting needles [ref:gubelin-koivula-vol1].
- Octahedral negative crystals are voids with the crystal habit of the host mineral —
+ Octahedral negative crystals are voids with the crystal habit of the host mineral –
a natural feature [ref:read-gemmology-3e].
- text: "Synthetic ruby; the high SG of 4.00 suggests flux contamination increased the density above natural ruby values"
isCorrect: false
rationale: |
- SG 4.00 is the standard value for natural ruby (corundum, Al2O3) — it is not
+ SG 4.00 is the standard value for natural ruby (corundum, Al2O3) – it is not
"above natural" and it does not indicate flux contamination [ref:read-gemmology-3e]. Flux-grown synthetic
ruby has the same SG as natural ruby because the host crystal is pure Al2O3;
any flux inclusions present would slightly lower SG rather than raise it [ref:read-gemmology-3e].
@@ -31,14 +31,14 @@ options:
isCorrect: false
rationale: |
The Verneuil (flame fusion) process does not use TiO2 as a dopant and does not
- produce true rutile silk [ref:read-gemmology-3e]. Verneuil rubies show characteristic curved growth striae —
+ produce true rutile silk [ref:read-gemmology-3e]. Verneuil rubies show characteristic curved growth striae –
fine curved lines visible under darkfield illumination, reflecting the curved
growth front of the boule [ref:gubelin-koivula-vol1]. They may contain minute gas bubbles and
occasionally unmelted powder. The presence of straight, intersecting rutile needles
at 60° is a natural formation indicator, not a Verneuil feature [ref:read-gemmology-3e].
rationaleCorrect: |
- The microscopic features described — rutile silk at 60° intersections and octahedral
- negative crystals — are both natural inclusion types that cannot be replicated by
+ The microscopic features described – rutile silk at 60° intersections and octahedral
+ negative crystals – are both natural inclusion types that cannot be replicated by
synthetic processes [ref:read-gemmology-3e]. Rutile silk arises from exsolution during slow geological cooling;
it is one of the most important natural origin indicators in corundum [ref:gubelin-koivula-vol1]. Synthetic rubies
have their own diagnostic inclusion suites: Verneuil shows curved growth striae and
diff --git a/src/content/questions/species/green-stone-001.yaml b/src/content/questions/species/green-stone-001.yaml
index aff0eb7..9417f5b 100644
--- a/src/content/questions/species/green-stone-001.yaml
+++ b/src/content/questions/species/green-stone-001.yaml
@@ -12,8 +12,8 @@ options:
- text: "Colombian emerald (beryl); three-phase inclusions with a halite cube are virtually diagnostic of Colombian origin; the jardin and two-phase inclusions confirm natural emerald"
isCorrect: true
rationale: |
- The three-phase inclusion — liquid + gas bubble + solid cubic crystal (halite,
- NaCl) — is one of the most celebrated diagnostic features in gemmology: it is
+ The three-phase inclusion – liquid + gas bubble + solid cubic crystal (halite,
+ NaCl) – is one of the most celebrated diagnostic features in gemmology: it is
virtually diagnostic of Colombian origin for emerald [ref:gubelin-koivula-vol1]. The RI ~1.58 (beryl range
1.577–1.583), SG 2.71 (beryl range 2.67–2.78) [ref:read-gemmology-3e], dichroism in blue-green and
yellow-green, and parallel growth tubes all confirm emerald [ref:read-gemmology-3e]. The jardin (from
@@ -22,14 +22,14 @@ options:
isCorrect: false
rationale: |
Chrome tourmaline (Cr-bearing elbaite/dravite) is vivid green with strong
- dichroism — correct. However, tourmaline RI is 1.620–1.640, not approximately
+ dichroism – correct. However, tourmaline RI is 1.620–1.640, not approximately
1.58 [ref:read-gemmology-3e]. A spot reading of 1.58 falls well below tourmaline's minimum RI.
- Three-phase inclusions with a halite cube are not a known feature of tourmaline —
+ Three-phase inclusions with a halite cube are not a known feature of tourmaline –
they are specific to the saline-fluid formation environment of Colombian emerald [ref:gubelin-koivula-vol1].
- text: "Tsavorite garnet (grossular); tsavorite is vivid green, has SG approximately 3.61, and shows strong dichroism"
isCorrect: false
rationale: |
- Tsavorite (chrome/vanadium grossular garnet) is cubic and therefore isotropic —
+ Tsavorite (chrome/vanadium grossular garnet) is cubic and therefore isotropic –
it shows no dichroism or pleochroism [ref:read-gemmology-3e]. The strong dichroism observed in this stone
eliminates any cubic gem, including all garnets. Additionally, tsavorite SG is
approximately 3.58–3.73, clearly higher than the measured 2.71 [ref:read-gemmology-3e]. The spot RI of
@@ -41,7 +41,7 @@ rationaleCorrect: |
evidence of Colombian origin [ref:gubelin-koivula-vol1]. The jardin of inclusions and two-phase cavities adds
supporting natural-origin evidence. Beryl RI 1.577–1.583, SG 2.67–2.78 confirms the
species [ref:read-gemmology-3e]. The dichroism (blue-green / yellow-green) is characteristic of Cr-bearing
- emerald [ref:read-gemmology-3e]. Note: UV response varies — some Colombian emeralds fluoresce, others do
+ emerald [ref:read-gemmology-3e]. Note: UV response varies – some Colombian emeralds fluoresce, others do
not, depending on iron content, so UV inertness does not exclude Colombia [ref:read-gemmology-3e].
difficulty: 4
category: species
diff --git a/src/content/questions/species/green-stone-002.yaml b/src/content/questions/species/green-stone-002.yaml
index 88bb940..ec9e1a0 100644
--- a/src/content/questions/species/green-stone-002.yaml
+++ b/src/content/questions/species/green-stone-002.yaml
@@ -11,7 +11,7 @@ options:
isCorrect: true
rationale: |
The RI range 1.620–1.637 is clearly above the maximum beryl RI of 1.583 by
- approximately 0.037 units — a large discrepancy on the refractometer [ref:read-gemmology-3e]. Beryl RI
+ approximately 0.037 units – a large discrepancy on the refractometer [ref:read-gemmology-3e]. Beryl RI
is 1.577–1.583 with birefringence 0.005–0.009; the measured birefringence of
~0.017 is too high for beryl [ref:read-gemmology-3e]. SG 3.06 matches tourmaline (SG 3.02–3.10) and is
well above beryl (2.67–2.78) [ref:read-gemmology-3e]. Chrome tourmaline (Cr-bearing elbaite) is a vivid
@@ -21,13 +21,13 @@ options:
rationale: |
Chromium content does not raise beryl's RI to 1.620–1.637. Chromium substitutes
for aluminium in the beryl structure and is present in concentrations of typically
- less than 1% — too little to measurably shift the RI away from the beryl range
+ less than 1% – too little to measurably shift the RI away from the beryl range
of 1.577–1.583 [ref:read-gemmology-3e]. An RI of 1.620–1.637 cannot be beryl of any composition.
- text: "Synthetic emerald (hydrothermal); hydrothermal emeralds have higher RI than natural beryl because the growth solution deposits additional silica in the lattice"
isCorrect: false
rationale: |
Hydrothermal synthetic emerald (Chatham, Biron, etc.) has essentially the same RI
- as natural beryl — approximately 1.560–1.570 (slightly lower than natural due to
+ as natural beryl – approximately 1.560–1.570 (slightly lower than natural due to
lower chromium and lower iron content relative to some natural emeralds) [ref:read-gemmology-3e]. The RI
of hydrothermal synthetic emerald is never 1.620–1.637; that range is tourmaline.
Additional silica in the lattice is not how hydrothermal growth affects RI, and the
@@ -35,8 +35,8 @@ options:
rationaleCorrect: |
Chrome tourmaline is the most important visual near-miss for fine emerald in the trade:
both are vivid green, both show dichroism, both can be found in similar size ranges
- and cuts. The discrimination is straightforward with instruments — beryl RI 1.577–1.583,
- tourmaline RI 1.620–1.640 [ref:read-gemmology-3e], a gap of approximately 0.04 units — but relies on the
+ and cuts. The discrimination is straightforward with instruments – beryl RI 1.577–1.583,
+ tourmaline RI 1.620–1.640 [ref:read-gemmology-3e], a gap of approximately 0.04 units – but relies on the
gemmologist actually measuring the RI rather than accepting the seller's description.
Chrome tourmaline offered as "Colombian emerald" has occurred in the trade. The SG
difference (beryl 2.67–2.78 vs tourmaline 3.06) [ref:read-gemmology-3e] provides additional confirmation.
diff --git a/src/content/questions/species/green-stone-003.yaml b/src/content/questions/species/green-stone-003.yaml
index bccec31..3767845 100644
--- a/src/content/questions/species/green-stone-003.yaml
+++ b/src/content/questions/species/green-stone-003.yaml
@@ -1,19 +1,19 @@
id: green-stone-003
stem: |
- A bright yellowish-green faceted stone is tested. Results: RI — no shadow edge on
- the standard refractometer (RI above contact-liquid limit); SG 3.84; polariscope —
- uniformly dark, isotropic; LWUV — moderate orange fluorescence; strong dispersion
+ A bright yellowish-green faceted stone is tested. Results: RI – no shadow edge on
+ the standard refractometer (RI above contact-liquid limit); SG 3.84; polariscope –
+ uniformly dark, isotropic; LWUV – moderate orange fluorescence; strong dispersion
visible as bright coloured flashes when the stone is tilted under a desk lamp.
The stone is set in a ring described as "demantoid." What is the most likely identity,
and why does the above-range refractometer reading not indicate diamond?
type: mcq
options:
- - text: "Demantoid garnet (andradite); cubic/isotropic with RI approximately 1.888 (above refractometer range), SG 3.82–3.85, highest dispersion of natural garnets (0.057) — the SG and dispersion confirm demantoid, not diamond (SG 3.52, inert LWUV)"
+ - text: "Demantoid garnet (andradite); cubic/isotropic with RI approximately 1.888 (above refractometer range), SG 3.82–3.85, highest dispersion of natural garnets (0.057) – the SG and dispersion confirm demantoid, not diamond (SG 3.52, inert LWUV)"
isCorrect: true
rationale: |
Demantoid (andradite garnet, Ca3Fe2(SiO4)3) is cubic and isotropic with RI
- approximately 1.855–1.900 — well above the standard refractometer limit of ~1.81 [ref:read-gemmology-3e].
- Its SG of 3.82–3.85 separates it from diamond (SG 3.52 — lighter, not heavier) [ref:read-gemmology-3e]
+ approximately 1.855–1.900 – well above the standard refractometer limit of ~1.81 [ref:read-gemmology-3e].
+ Its SG of 3.82–3.85 separates it from diamond (SG 3.52 – lighter, not heavier) [ref:read-gemmology-3e]
and confirms the garnet identification. The dispersion of 0.057 is the highest
of any natural garnet [ref:read-gemmology-3e] and produces vivid fire visible as coloured flashes.
Diamond has dispersion 0.044 (lower than demantoid) [ref:read-gemmology-3e] and is inert to LWUV.
@@ -21,7 +21,7 @@ options:
isCorrect: false
rationale: |
Tsavorite (green grossular) has RI approximately 1.740–1.760, which IS within the
- standard refractometer range — it gives a clear shadow edge in the 1.740–1.760
+ standard refractometer range – it gives a clear shadow edge in the 1.740–1.760
region [ref:read-gemmology-3e]. Tsavorite does not exceed the refractometer limit. Additionally, tsavorite
SG is approximately 3.57–3.73, clearly lower than the measured 3.84 [ref:read-gemmology-3e].
- text: "Diamond; colourless diamonds can appear green from colouring inclusions, and the above-range RI and isotropic behaviour both confirm diamond"
@@ -29,15 +29,15 @@ options:
rationale: |
Diamond SG is 3.52, clearly below the measured 3.84 [ref:read-gemmology-3e]. Diamond dispersion is 0.044,
lower than the dramatic fire described (consistent with demantoid's 0.057) [ref:read-gemmology-3e]. Diamond
- is inert to LWUV (or shows blue LWUV fluorescence) — orange LWUV is not a diamond
+ is inert to LWUV (or shows blue LWUV fluorescence) – orange LWUV is not a diamond
response [ref:read-gemmology-3e]. The SG is the decisive test: at SG 3.84, the stone is denser than
diamond [ref:read-gemmology-3e].
rationaleCorrect: |
Demantoid identification relies on the combination of: (1) above-range refractometer
(RI ~1.89, beyond contact-liquid limit) [ref:read-gemmology-3e]; (2) cubic/isotropic on polariscope;
- (3) SG 3.82–3.85 — heavier than diamond (3.52) [ref:read-gemmology-3e], which is a key discriminator;
+ (3) SG 3.82–3.85 – heavier than diamond (3.52) [ref:read-gemmology-3e], which is a key discriminator;
(4) high dispersion producing vivid fire (0.057, higher than diamond's 0.044) [ref:read-gemmology-3e];
- (5) characteristic "horsetail" inclusions under the microscope — byssolite/actinolite
+ (5) characteristic "horsetail" inclusions under the microscope – byssolite/actinolite
fibres radiating from a chromite crystal, virtually diagnostic for demantoid [ref:gubelin-koivula-vol1].
The absence of a refractometer reading is often the first clue: always go to SG and
microscopy next when the refractometer gives no reading on a green isotropic stone.
diff --git a/src/content/questions/species/green-stone-004.yaml b/src/content/questions/species/green-stone-004.yaml
index b886801..3675f76 100644
--- a/src/content/questions/species/green-stone-004.yaml
+++ b/src/content/questions/species/green-stone-004.yaml
@@ -3,13 +3,13 @@ stem: |
A laboratory tests an emerald-green oval brilliant with an RI of 1.577–1.582 and
SG of 2.69. Under the microscope the gemmologist sees numerous two-phase fluid
inclusions, some irregular growth cavities, and short three-sided hollow channels
- parallel to the crystal's c-axis — but no three-phase inclusions containing solid
+ parallel to the crystal's c-axis – but no three-phase inclusions containing solid
crystals. LWUV shows a moderate red fluorescence. An assistant concludes: "Absence
of three-phase inclusions proves this is NOT Colombian emerald." Is the assistant
correct?
type: mcq
options:
- - text: "The assistant is incorrect; three-phase inclusions are diagnostic FOR Colombian origin when present, but their absence does not exclude Colombia — not all Colombian emeralds contain them, and other tests (UV, RI, SG) remain consistent with Colombian beryl"
+ - text: "The assistant is incorrect; three-phase inclusions are diagnostic FOR Colombian origin when present, but their absence does not exclude Colombia – not all Colombian emeralds contain them, and other tests (UV, RI, SG) remain consistent with Colombian beryl"
isCorrect: true
rationale: |
Three-phase inclusions are characteristic of Colombian emerald and, when present,
@@ -17,8 +17,8 @@ options:
does not exclude Colombia: not every Colombian emerald contains three-phase inclusions,
and some sections of a stone may lack them even when present elsewhere [ref:read-gemmology-3e]. Three-phase
inclusions are a positive indicator, not a required feature. The correct approach
- is to state "no three-phase inclusions observed" in the report — a neutral
- observation — while noting that the RI (1.577–1.582), SG (2.69) [ref:read-gemmology-3e], red LWUV
+ is to state "no three-phase inclusions observed" in the report – a neutral
+ observation – while noting that the RI (1.577–1.582), SG (2.69) [ref:read-gemmology-3e], red LWUV
fluorescence, and growth-tube features are all consistent with Colombian beryl.
- text: "The assistant is correct; three-phase inclusions are virtually diagnostic for Colombia, so their absence provides equal and opposite evidence that the stone is not Colombian"
isCorrect: false
@@ -33,7 +33,7 @@ options:
- text: "The assistant is correct, but for the wrong reason; the absence of three-phase inclusions proves the stone is synthetic emerald, which never contains three-phase inclusions"
isCorrect: false
rationale: |
- Synthetic emeralds do not produce three-phase inclusions containing halite —
+ Synthetic emeralds do not produce three-phase inclusions containing halite –
this is correct [ref:gubelin-koivula-vol1]. However, many natural non-Colombian emeralds also lack
three-phase inclusions (Zambian, Brazilian, Ethiopian, Afghan emeralds have
different inclusion suites) [ref:gubelin-koivula-vol1]. The absence of three-phase inclusions does not
@@ -45,7 +45,7 @@ rationaleCorrect: |
This question addresses a common logical error in gemmology: the confusion between
a positive indicator and a required indicator. Three-phase inclusions in emerald are
a positive diagnostic for Colombian origin when present, but their absence is not
- a negative diagnostic [ref:gubelin-koivula-vol1]. Colombian origin is established through a weight of evidence —
+ a negative diagnostic [ref:gubelin-koivula-vol1]. Colombian origin is established through a weight of evidence –
microscopy, UV fluorescence, RI, SG [ref:read-gemmology-3e], and where necessary trace-element analysis
(e.g. LA-ICP-MS at a major laboratory). The red LWUV fluorescence (Cr-bearing beryl),
RI and SG within the beryl range [ref:read-gemmology-3e], and natural inclusion types are all consistent
diff --git a/src/content/questions/species/green-stone-005.yaml b/src/content/questions/species/green-stone-005.yaml
index 06cd5f8..3001242 100644
--- a/src/content/questions/species/green-stone-005.yaml
+++ b/src/content/questions/species/green-stone-005.yaml
@@ -13,7 +13,7 @@ options:
rationale: |
Emerald (beryl) RI 1.577–1.583 with minimum value 1.577 [ref:read-gemmology-3e]; the measured 1.54 is
approximately 0.037 below the minimum beryl value. This single reading eliminates
- emerald absolutely — no beryl of any composition gives RI as low as 1.54 [ref:read-gemmology-3e]. Green
+ emerald absolutely – no beryl of any composition gives RI as low as 1.54 [ref:read-gemmology-3e]. Green
glass RI can be approximately 1.50–1.55 depending on composition [ref:read-gemmology-3e]. SG ~2.50 is
consistent with light glass (beryl SG is 2.67–2.78, also higher) [ref:read-gemmology-3e]. The featureless,
homogeneous interior (no growth features, no inclusions) is typical of glass.
@@ -21,8 +21,8 @@ options:
isCorrect: false
rationale: |
The SG is a secondary confirmatory observation, not the most immediate eliminator
- in this case. SG of green glass varies considerably — from approximately 2.3 for
- borosilicate to 4.5+ for high-lead glass [ref:read-gemmology-3e] — depending on composition. Stating that
+ in this case. SG of green glass varies considerably – from approximately 2.3 for
+ borosilicate to 4.5+ for high-lead glass [ref:read-gemmology-3e] – depending on composition. Stating that
glass "always reads 2.50" is incorrect. The RI reading is the most immediately
accessible and precise measurement: the refractometer is used first in the standard
workflow, and the 1.54 reading eliminates beryl with a 0.037-unit margin [ref:read-gemmology-3e].
@@ -34,7 +34,7 @@ options:
test is not binary: some Cr-bearing emeralds (especially vanadium-rich or iron-rich
varieties) may not respond strongly red [ref:read-gemmology-3e], and some non-emerald green materials
(Cr-bearing glass) appear red. A green response under the Chelsea filter does not
- rule out Cr-bearing emerald — it is a screening tool, not a definitive test [ref:read-gemmology-3e].
+ rule out Cr-bearing emerald – it is a screening tool, not a definitive test [ref:read-gemmology-3e].
rationaleCorrect: |
Spot RI 1.54 is the critical reading here: it is below the minimum RI of any beryl
(1.577), eliminating emerald with certainty [ref:read-gemmology-3e]. The RI measurement is the most immediate
diff --git a/src/content/questions/species/red-stone-garnet-001.yaml b/src/content/questions/species/red-stone-garnet-001.yaml
index 9704545..298d8de 100644
--- a/src/content/questions/species/red-stone-garnet-001.yaml
+++ b/src/content/questions/species/red-stone-garnet-001.yaml
@@ -12,7 +12,7 @@ options:
isCorrect: true
rationale: |
Almandine (Fe-Al garnet) is cubic and isotropic, with RI typically 1.770–1.830
- and SG 3.9–4.2 [ref:read-gemmology-3e] — the measured 1.75 and 3.82 fall within the lower end of almandine
+ and SG 3.9–4.2 [ref:read-gemmology-3e] – the measured 1.75 and 3.82 fall within the lower end of almandine
or could indicate a pyrope-almandine intermediate (rhodolite). The single constant
edge confirms isotropic (cubic) behaviour. The patchy, irregular lightening on the
polariscope is anomalous double refraction (ADR): strain birefringence from growth
@@ -22,7 +22,7 @@ options:
isCorrect: false
rationale: |
A uniaxial stone examined exactly down its optic axis (the c-axis) would appear
- uniformly dark between crossed polars — it would not show patchy, irregular
+ uniformly dark between crossed polars – it would not show patchy, irregular
lightening [ref:read-gemmology-3e]. Patchy lightening is specifically the pattern of ADR (anomalous double
refraction) in cubic minerals, not the pattern of a uniaxial stone viewed down
its optic axis. Moreover, ruby has RI 1.762–1.770 and SG 3.99–4.01 [ref:read-gemmology-3e]; the measured
@@ -41,7 +41,7 @@ rationaleCorrect: |
Almandine garnet (or pyrope-almandine rhodolite) is the correct identification.
The single constant shadow edge confirms isotropic (cubic) behaviour [ref:read-gemmology-3e]; the RI ~1.75
and SG 3.82 are consistent with almandine or a pyrope-rich intermediate. The patchy
- polariscope response is anomalous double refraction (ADR) — a strain birefringence
+ polariscope response is anomalous double refraction (ADR) – a strain birefringence
effect common in cubic garnets, particularly almandine [ref:read-gemmology-3e]. ADR looks like irregular
patches of light and dark rather than the systematic four-fold lightening of a doubly
refractive gem. The absence of LWUV fluorescence is typical for iron-bearing garnet [ref:read-gemmology-3e].
diff --git a/src/content/questions/species/red-stone-glass-001.yaml b/src/content/questions/species/red-stone-glass-001.yaml
index 98040ee..eac8e61 100644
--- a/src/content/questions/species/red-stone-glass-001.yaml
+++ b/src/content/questions/species/red-stone-glass-001.yaml
@@ -12,10 +12,10 @@ options:
isCorrect: true
rationale: |
RI approximately 1.59 is far below ruby (1.762–1.770) [ref:read-gemmology-3e], spinel (1.712–1.720) [ref:read-gemmology-3e], and
- almandine garnet (1.770–1.830) [ref:read-gemmology-3e] — all three cannot produce this reading. The value
+ almandine garnet (1.770–1.830) [ref:read-gemmology-3e] – all three cannot produce this reading. The value
1.59 falls within the range for silicate glass (typically 1.44–1.70 depending on
- composition) [ref:read-gemmology-3e]. Foiled settings — metal foil behind the stone to enhance brightness
- — were a standard technique for glass stones in Georgian and early Victorian
+ composition) [ref:read-gemmology-3e]. Foiled settings – metal foil behind the stone to enhance brightness
+ – were a standard technique for glass stones in Georgian and early Victorian
jewellery before synthetic stones became available [ref:read-gemmology-3e]. The isotropic polariscope
result is consistent with amorphous glass.
- text: "Natural ruby; Georgian jewellers often cut rubies with foiled settings to enhance the colour, and heat treatment has reduced the RI to 1.59"
@@ -23,7 +23,7 @@ options:
rationale: |
Heat treatment does not alter the RI or crystal structure of corundum. Ruby RI is
determined by the Al2O3 crystal lattice and cannot be changed by any thermal
- treatment to reach 1.59 — a difference of over 0.17 from corundum's 1.762 [ref:read-gemmology-3e]. Foiled
+ treatment to reach 1.59 – a difference of over 0.17 from corundum's 1.762 [ref:read-gemmology-3e]. Foiled
settings were not typically used for genuine rubies in Georgian jewellery; they
were used for glass, paste, and composite stones to improve brilliance where the
material's own lustre was insufficient [ref:read-gemmology-3e].
@@ -31,7 +31,7 @@ options:
isCorrect: false
rationale: |
The Verneuil flame-fusion process was developed by Auguste Verneuil and became
- commercially available approximately 1902 — well after the Georgian era
+ commercially available approximately 1902 – well after the Georgian era
(approximately 1714–1830) [ref:read-gemmology-3e]. Georgian jewellers did not have access to synthetic
ruby. More importantly, Verneuil synthetic ruby has exactly the same RI as natural
ruby (1.762–1.770) because it is chemically identical Al2O3 [ref:read-gemmology-3e]. No form of synthetic
diff --git a/src/layouts/BaseLayout.astro b/src/layouts/BaseLayout.astro
index c86ad2c..f46b6ac 100644
--- a/src/layouts/BaseLayout.astro
+++ b/src/layouts/BaseLayout.astro
@@ -16,7 +16,7 @@ interface Props {
const {
title,
- description = 'Crystal structure visualization and gemmological reference for FGA students and professionals.',
+ description = 'Crystal structure visualisation and gemmological reference for FGA students and professionals.',
image,
canonical,
type = 'website',
@@ -35,8 +35,8 @@ const ogImage = image || new URL('/og-default.jpg', Astro.site).href;
// brand IS the title (avoids "gemmology.dev — gemmology.dev" duplication).
const isHome = Astro.url.pathname === '/' || Astro.url.pathname === '';
const fullTitle = isHome
- ? `gemmology.dev — Crystal Visualization & FGA Reference`
- : `gemmology.dev — ${title}`;
+ ? `gemmology.dev – Crystal Visualisation & FGA Reference`
+ : `gemmology.dev – ${title}`;
---
diff --git a/src/pages/_dev/study-components.astro b/src/pages/_dev/study-components.astro
index 7ba2b26..ef0d6de 100644
--- a/src/pages/_dev/study-components.astro
+++ b/src/pages/_dev/study-components.astro
@@ -21,7 +21,7 @@ if (!import.meta.env.DEV) {
-
Study Components — Dev Harness
+
Study Components: Dev Harness
diff --git a/src/pages/about.astro b/src/pages/about.astro
index 59c5b7f..bf0fffa 100644
--- a/src/pages/about.astro
+++ b/src/pages/about.astro
@@ -11,7 +11,7 @@ const { familyCount, expressionCount } = await getSiteStats();
About gemmology.dev
gemmology.dev is an open, FGA-aligned reference and study toolkit for
- coloured gemstones. Everything here — the {familyCount}-mineral family
+ coloured gemstones. Everything here – the {familyCount}-mineral family
reference, {expressionCount} crystal expressions, the Crystal
- Description Language (CDL), the calculators, and the quiz — is
+ Description Language (CDL), the calculators, and the quiz – is
free and open-source.
@@ -64,8 +64,8 @@ const { familyCount, expressionCount } = await getSiteStats();
Crystal morphology. Crystal structures are described
- using CDL — a domain-specific language documented at
-
@@ -94,15 +94,15 @@ const { familyCount, expressionCount } = await getSiteStats();
Commercial appraisals or price guidance
Real-time market or auction data
- Authentication or certification — gemmology.dev is a study tool, not a lab
+ Authentication or certification: gemmology.dev is a study tool, not a lab
Reporting an error
Spotted incorrect data, a missing reference, or a broken figure?
Open an issue at
- github.com/gemmology-dev/gemmology.dev/issues
- — corrections are usually shipped within a week.
+ github.com/gemmology-dev/gemmology.dev/issues .
+ Corrections are usually shipped within a week.
Licence
diff --git a/src/pages/docs/api/cdl-parser.astro b/src/pages/docs/api/cdl-parser.astro
index 35c73ae..87132ae 100644
--- a/src/pages/docs/api/cdl-parser.astro
+++ b/src/pages/docs/api/cdl-parser.astro
@@ -212,7 +212,7 @@ print(doc_comments) # ['Mineral: Diamond', 'System: Cubic']`}
CrystalDescriptionThe main output of CDL parsing, containing all information needed
- to generate a crystal visualization.
+ to generate a crystal visualisation.
crystal-renderer
- Render crystal geometry to SVG for visualization, STL for 3D printing,
+ Render crystal geometry to SVG for visualisation, STL for 3D printing,
and glTF for web/AR/VR applications. Version 1.0.1.
@@ -67,7 +67,7 @@ const geometrySvgParams = [
signature="generate_cdl_svg(cdl_string, output_path, **options) → Path"
/>
- Generate an SVG visualization directly from a CDL string. This is the primary
+
Generate an SVG visualisation directly from a CDL string. This is the primary
rendering function - it parses the CDL, generates geometry, and renders to SVG
in one call.
@@ -256,7 +256,7 @@ convert_svg_to_raster("crystal.svg", "crystal.jpg", output_format="jpg", quality
signature="generate_with_format(generator_func, output_path, output_format='svg', scale=2.0, quality=95, **kwargs) → Path"
/>
- Generate a crystal visualization in any supported format. Wraps a generator
+
Generate a crystal visualisation in any supported format. Wraps a generator
function, automatically converting through SVG for raster outputs.
Info Panel
@@ -277,7 +277,7 @@ convert_svg_to_raster("crystal.svg", "crystal.jpg", output_format="jpg", quality
Rendering Primitives
- Low-level drawing functions for building custom visualizations:
+ Low-level drawing functions for building custom visualisations:
CDL is a domain-specific language for describing crystal morphology using crystallographic
notation. It combines crystal systems, point groups, Miller indices, and optional modifiers
- to precisely define crystal forms for 3D visualization.
+ to precisely define crystal forms for 3D visualisation.
diff --git a/src/pages/docs/cli.astro b/src/pages/docs/cli.astro
index b795751..0acb1f5 100644
--- a/src/pages/docs/cli.astro
+++ b/src/pages/docs/cli.astro
@@ -7,7 +7,7 @@ import { Container, Card } from '../../components/ui-astro';
The gemmology ecosystem provides three CLI tools for parsing CDL expressions,
- querying the mineral database, and generating crystal visualizations.
+ querying the mineral database, and generating crystal visualisations.
cdl - CDL Parser CLIThe gemmology command is installed with the plugin package and provides
- crystal visualization from the terminal.
+ crystal visualisation from the terminal.
Basic Usage
diff --git a/src/pages/docs/index.astro b/src/pages/docs/index.astro
index 724deed..8585a25 100644
--- a/src/pages/docs/index.astro
+++ b/src/pages/docs/index.astro
@@ -10,7 +10,7 @@ const sections = [
title: 'Getting Started',
items: [
{ href: '/docs/installation', label: 'Installation', description: 'Install gemmology packages via pip' },
- { href: '/docs/quickstart', label: 'Quick Start', description: 'Generate your first crystal visualization' },
+ { href: '/docs/quickstart', label: 'Quick Start', description: 'Generate your first crystal visualisation' },
],
},
{
@@ -48,7 +48,7 @@ const sections = [
Documentation
- Everything you need to create crystal visualizations with gemmology.dev packages.
+ Everything you need to create crystal visualisations with gemmology.dev packages.
diff --git a/src/pages/docs/installation.astro b/src/pages/docs/installation.astro
index 02757fd..990b56c 100644
--- a/src/pages/docs/installation.astro
+++ b/src/pages/docs/installation.astro
@@ -7,7 +7,7 @@ import { Container, Button } from '../../components/ui-astro';
Quick Start
- Generate your first crystal visualization in just a few lines of Python code.
+ Generate your first crystal visualisation in just a few lines of Python code.
Your First Crystal
diff --git a/src/pages/index.astro b/src/pages/index.astro
index 16d98cc..08650f3 100644
--- a/src/pages/index.astro
+++ b/src/pages/index.astro
@@ -17,7 +17,7 @@ const websiteSchema = {
"@context": "https://schema.org",
"@type": "WebSite",
"name": "gemmology.dev",
- "description": "Crystal structure visualization and gemmological reference for FGA students and professionals.",
+ "description": "Crystal structure visualisation and gemmological reference for FGA students and professionals.",
"url": "https://gemmology.dev",
"potentialAction": {
"@type": "SearchAction",
@@ -43,7 +43,7 @@ const organizationSchema = {
const features = [
{
title: 'Crystal Gallery',
- description: `Explore ${familyCount} mineral families and ${expressionCount} crystal expressions with FGA-accurate data and interactive visualizations.`,
+ description: `Explore ${familyCount} mineral families and ${expressionCount} crystal expressions with FGA-accurate data and interactive visualisations.`,
href: '/gallery',
icon: 'gallery',
variant: 'crystal' as const,
@@ -90,7 +90,7 @@ const iconPaths: Record = {
};
---
-
+
diff --git a/src/pages/learn/index.astro b/src/pages/learn/index.astro
index d2dc0ca..da7e7ec 100644
--- a/src/pages/learn/index.astro
+++ b/src/pages/learn/index.astro
@@ -219,7 +219,7 @@ const iconPaths: Record = {
Start here
- — recommended foundations before you dive in
+ Recommended foundations to read first
{startHereTopics.map((topic, i) => (
diff --git a/src/pages/og-image.astro b/src/pages/og-image.astro
index 7aad534..8e8e973 100644
--- a/src/pages/og-image.astro
+++ b/src/pages/og-image.astro
@@ -105,7 +105,7 @@
gap: 60px;
}
- /* Left side - Crystal visualization */
+ /* Left side - Crystal visualisation */
.crystal-section {
display: flex;
align-items: center;
@@ -288,7 +288,7 @@
-
+
@@ -349,7 +349,7 @@
Crystal Structure
diff --git a/src/pages/study/review.astro b/src/pages/study/review.astro
index 40a6b99..961decb 100644
--- a/src/pages/study/review.astro
+++ b/src/pages/study/review.astro
@@ -24,7 +24,7 @@ const entries: LearnEntry[] = learnEntries.map(entry => ({