diff --git a/docs/learn/equipment/other-tools.yaml b/docs/learn/equipment/other-tools.yaml index c7a4029..2636f35 100644 --- a/docs/learn/equipment/other-tools.yaml +++ b/docs/learn/equipment/other-tools.yaml @@ -203,7 +203,7 @@ sections: - ["Water (baseline)", "1.00", "None (all gems sink)", "All gemstones", "Safe"] - ["Toluene", "0.87", "Amber (SG 0.96–1.10)", "All other gems", "Toxic fumes — use fume hood"] - ["Bromoform", "2.89", "Quartz, feldspar, beryl, opal", "Tourmaline, diamond, corundum", "Toxic — use gloves"] - - ["Methylene iodide (pure)", "3.32", "Quartz, beryl, tourmaline", "Diamond, corundum, spinel, topaz", "Very toxic — gloves + fume hood"] + - ["Methylene iodide (pure)", "3.33", "Quartz, beryl, tourmaline", "Diamond, corundum, spinel, topaz", "Very toxic — gloves + fume hood"] - ["MI + toluene (diluted)", "3.06", "Quartz, beryl, tourmaline hovers", "Diamond, corundum, topaz", "Toxic — gloves + fume hood"] - ["Clerici solution", "4.25", "Diamond, corundum, topaz, spinel", "Zircon, cassiterite", "Toxic and corrosive"] @@ -214,7 +214,7 @@ sections: - Gem - SG - Bromoform (2.89) - - MI (3.32) + - MI (3.33) - Clerici (4.25) rows: - ["Amber", "1.08", "Floats", "Floats", "Floats"] diff --git a/docs/learn/equipment/polariscope.yaml b/docs/learn/equipment/polariscope.yaml index 40025ca..e2dd8af 100644 --- a/docs/learn/equipment/polariscope.yaml +++ b/docs/learn/equipment/polariscope.yaml @@ -54,7 +54,7 @@ sections: rows: - ["Remains dark during rotation", "Isotropic (cubic system or amorphous)", "Diamond, spinel, garnet, glass"] - ["Light and dark every 90° (4× blink)", "Anisotropic (crystalline, non-cubic)", "Quartz, tourmaline, corundum, beryl"] - - ["Remains light (never dark)", "Aggregate or microcrystalline material", "Jade (jadeite/nephrite), chalcedony"] + - ["Remains light (never dark)", "Aggregate or microcrystalline material — but note: some types of glass also remain light throughout rotation; confirm with magnification or RI (Source: Gem-A D6-23)", "Jade (jadeite/nephrite), chalcedony; also some glass"] - ["Patchy light/dark (tabby extinction)", "ADR or strain birefringence", "Strained garnet, synthetic spinel"] - title: Anomalous Double Refraction (ADR) diff --git a/docs/learn/equipment/refractometer.yaml b/docs/learn/equipment/refractometer.yaml index 58d7447..c633a10 100644 --- a/docs/learn/equipment/refractometer.yaml +++ b/docs/learn/equipment/refractometer.yaml @@ -34,8 +34,8 @@ sections: content: | A standard gemmological refractometer includes: - - **High-RI glass hemisphere**: Typically RI ~1.86 - - **Contact liquid** (RI ~1.81): Bridges the gap between gem and glass + - **High-RI glass hemisphere**: Typically RI ~1.86; the dense glass sets the upper limit of the measurement scale (~1.81) + - **Contact liquid** (di-iodomethane / methylene iodide, RI approximately 1.74): Bridges the gap between gem and glass (Source: Gem-A D6-26) - **Scale**: Range typically 1.35–1.81 - **Light source**: Monochromatic sodium yellow (589nm) for accurate readings - **Eyepiece**: For viewing the scale and shadow edge @@ -177,7 +177,7 @@ sections: - Possible Cause - Solution rows: - - ["No reading visible", "RI above contact liquid limit (>1.81)", "Use SG or other tests; stone may be diamond, zircon, etc."] + - ["No reading visible", "RI above the hemisphere glass limit (>1.81); contact liquid RI is ~1.74", "Use SG or other tests; stone may be diamond, zircon, etc."] - ["Fuzzy edge", "Birefringent stone, dirty contact, poor polish", "Clean surface; rotate stone; check polish"] - ["Moving readings", "High birefringence", "Rotate and record both extreme values"] - ["Very faint reading", "Poor lighting or positioning", "Improve lighting; reposition stone"] @@ -188,7 +188,7 @@ sections: type: warning title: Handling Contact Liquid text: | - Standard contact liquid (methylene iodide, RI ~1.74-1.81) requires careful handling: + Standard contact liquid (di-iodomethane / methylene iodide, RI approximately 1.74) requires careful handling. Note: the 1.81 upper limit refers to the dense glass hemisphere, not the contact liquid itself. - **Toxic**: Avoid skin contact and inhalation - **Light sensitive**: Store in dark bottles diff --git a/docs/learn/equipment/spectroscope.yaml b/docs/learn/equipment/spectroscope.yaml index 5812984..5121661 100644 --- a/docs/learn/equipment/spectroscope.yaml +++ b/docs/learn/equipment/spectroscope.yaml @@ -90,7 +90,7 @@ sections: - ["Blue sapphire", "Fe bands", "450, 460, 470 (three-band)"] - ["Almandine garnet", "Fe bands", "505, 520, 575 (diagnostic trio)"] - ["Zircon (high)", "Uranium lines", "Many fine lines throughout spectrum"] - - ["Demantoid garnet", "Cr line", "443 (horse line; diagnostic)"] + - ["Demantoid garnet", "Fe³⁺ doublet (438/444 nm; present in all andradite regardless of Cr content)", "443 (horse line; diagnostic — Fe³⁺, not Cr; Cr causes green colour via 618 nm and ~700 nm absorption)"] - ["Peridot", "Fe bands", "493, 473, 453 (three evenly spaced)"] - ["Yellow sapphire", "Fe bands", "450 band region"] - ["Yellow apatite", "Rare earth lines", "Multiple fine lines in yellow-green"] diff --git a/docs/learn/fundamentals/chemical-properties.yaml b/docs/learn/fundamentals/chemical-properties.yaml index ef70b97..b66ad02 100644 --- a/docs/learn/fundamentals/chemical-properties.yaml +++ b/docs/learn/fundamentals/chemical-properties.yaml @@ -78,8 +78,13 @@ sections: - **Chrome tourmaline**: Green tourmaline - **Tsavorite**: Green grossular garnet - Chromium typically produces red in oxide minerals and green in silicates, - though the host mineral structure affects the exact colour. + The colour Cr³⁺ imparts depends on the crystal-field environment: shorter + Cr–O bond distances and stronger crystal-field splitting (as in ruby, Cr in + corundum lattice) shift absorption toward red transmission; longer bonds and + weaker fields (as in emerald, Cr in beryl lattice) shift toward green + transmission. The simple oxide-vs-silicate rule fails — red spinel is an + oxide, yet the absorption pattern matches the field environment, not the + anion class. (Source: Gem-A D7-24.) - title: Iron (Fe²⁺ and Fe³⁺) content: | diff --git a/docs/learn/fundamentals/crystal-systems.yaml b/docs/learn/fundamentals/crystal-systems.yaml index c5d5154..12a3d62 100644 --- a/docs/learn/fundamentals/crystal-systems.yaml +++ b/docs/learn/fundamentals/crystal-systems.yaml @@ -121,14 +121,14 @@ sections: - title: Orthorhombic system: orthorhombic cdl: "orthorhombic[mmm]:{110}@1.0+{010}@1.2+{001}@0.8" - content: Three twofold axes or two mirror planes. + content: Three two-fold axes (or three two-fold axes plus three mirror planes for the holohedral class). items: - name: Axes value: "a ≠ b ≠ c" - name: Angles value: "α = β = γ = 90°" - name: Minimum Symmetry - value: "3 twofold axes or 2 planes" + value: "three two-fold axes (or three two-fold axes plus three mirror planes for the holohedral class)" - name: Point Groups value: "mmm, 222, mm2" - name: Example Gems diff --git a/docs/learn/fundamentals/crystallography-advanced.yaml b/docs/learn/fundamentals/crystallography-advanced.yaml index ed56def..b923c61 100644 --- a/docs/learn/fundamentals/crystallography-advanced.yaml +++ b/docs/learn/fundamentals/crystallography-advanced.yaml @@ -163,7 +163,7 @@ sections: text: | Twinning affects optical properties and can complicate identification: - - Polysynthetic twinning causes labradorescence in labradorite + - Bøggild exsolution lamellae (not mechanical twinning) cause labradorescence in labradorite - Brazil twinning in quartz creates optical irregularities - Twin planes can be mistaken for cleavage - Twinning may cause anomalous optical behaviour under polariscope @@ -259,9 +259,22 @@ sections: - ["Hexagonal", "6/mmm", "Beryl"] - ["Hexagonal", "6mm", "Wurtzite"] - ["Hexagonal", "6/m", "Apatite"] - - ["Trigonal", "-3m", "Corundum, tourmaline"] + - ["Trigonal", "-3m", "Corundum"] - ["Trigonal", "32", "Quartz"] - - ["Trigonal", "3m", "Dioptase"] + - ["Trigonal", "3m", "Tourmaline, dioptase"] + + - title: Acentric Point Groups — Tourmaline vs Corundum + callout: + type: info + title: Tourmaline is Acentric (3m); Corundum is Centrosymmetric (-3m) + text: | + Tourmaline is acentric (point group 3m), which is why it exhibits + pyroelectricity and piezoelectricity. Corundum (-3m) is centrosymmetric + and therefore neither pyroelectric nor piezoelectric. Although both + minerals belong to the trigonal system, the presence or absence of a + centre of symmetry controls these physical effects. + + Source: Gem-A D3 crystal systems; standard crystallography references. - title: Crystal Growth content: | diff --git a/docs/learn/identification/synthetics.yaml b/docs/learn/identification/synthetics.yaml index d8578a4..8a65085 100644 --- a/docs/learn/identification/synthetics.yaml +++ b/docs/learn/identification/synthetics.yaml @@ -183,7 +183,7 @@ sections: rows: - ["1902", "Verneuil (flame fusion) process", "First commercial synthetic ruby"] - ["1917", "Czochralski pulling method", "Single crystals from melt"] - - ["1928", "Flux-grown emerald (IG Farben)", "First synthetic emerald"] + - ["c. 1935", "Flux-grown emerald (Espig / IG Farben)", "Earliest reliably-sourced experimental flux emerald. Note: some references give 1928; Gem-A Journal of Gemmology (Zerfass) puts general availability in the 1930s."] - ["1953", "HPHT diamond (GE)", "First reproducible synthetic diamond"] - ["1963", "Chatham flux-grown ruby", "Commercial flux synthetics"] - ["1965", "Linde star sapphire", "Synthetic star corundum"] @@ -221,7 +221,7 @@ sections: - **Doubling**: Strong birefringence shows facet doubling under magnification - **Electrical conductivity**: Moissanite conducts; diamond doesn't (except Type IIb) - - **Specific gravity**: Lower than diamond (floats in 3.32 heavy liquid) + - **Specific gravity**: Lower than diamond (floats in 3.33 MI heavy liquid) - **Needle-like inclusions**: White, parallel needles common - **Thermal-electrical testers**: Dual-function testers identify moissanite diff --git a/docs/learn/origin/burma/ruby.yaml b/docs/learn/origin/burma/ruby.yaml index 3991b12..6c5fbc8 100644 --- a/docs/learn/origin/burma/ruby.yaml +++ b/docs/learn/origin/burma/ruby.yaml @@ -77,7 +77,7 @@ sections: content: | Myanmar's other major ruby source: - - **Location**: Shan State, discovered 1990s + - **Location**: Shan State, discovered 1992; first stones appeared in Bangkok mid-1992 (Hughes; Peretti et al. G&G Spring 1995) - **Character**: Often dark cores with saturated edges - **Treatment**: Most material heat-treated - **Volume**: Major production; lower quality average diff --git a/docs/learn/origin/kashmir.yaml b/docs/learn/origin/kashmir.yaml index c04b7f9..cae300b 100644 --- a/docs/learn/origin/kashmir.yaml +++ b/docs/learn/origin/kashmir.yaml @@ -82,7 +82,7 @@ sections: rows: - ["Tourmaline crystals", "Black prismatic crystals (schorl); diagnostic"] - ["Zircon with halos", "Zircon crystals with tension fractures"] - - ["Pargasite", "Amphibole needles"] + - ["Pargasite", "Calcium amphibole; occurs as needles/prisms — diagnostic of Kashmir origin (Schwieger G&G 1990; Hughes 1997; Lotus Gemology Crystal Registry)"] - ["Fine particulates", "Microscopic particles causing haziness"] - ["Colour zoning", "Irregular blue/colourless zones"] - ["Fingerprints", "Healed fractures with fluid remnants"] diff --git a/docs/learn/phenomena/adularescence.yaml b/docs/learn/phenomena/adularescence.yaml index 03dcc06..0ddd014 100644 --- a/docs/learn/phenomena/adularescence.yaml +++ b/docs/learn/phenomena/adularescence.yaml @@ -30,10 +30,16 @@ sections: subsections: - title: Feldspar Structure content: | - Moonstone is a feldspar with alternating layers of orthoclase and albite - created during slow cooling (exsolution). When these layers are thin - enough (approaching the wavelength of light), they scatter light through - interference. + Adularescence in moonstone arises from light scattering combined with + thin-film interference at sub-micron alternating lamellae of orthoclase + and albite (Bøggild-style exsolution intergrowth, lamellae ~50–500 nm). + The blue/silvery sheen is wavelength-selective scattering plus partial + interference reinforcement. Earlier descriptions as "pure scattering" + (Gem-A D7 p. D7-31) or "pure thin-film interference" both capture only + one half of the mechanism. + + Sources: Gem-A D7 p. D7-31; Gem-A Gem Hub article "Understanding + Moonstones and Adularescence" (Pat Daly, 2023). - title: Layer Thickness and Colour content: | @@ -121,7 +127,7 @@ sections: - Multiple spectral colours - Sharp, distinct flashes - Appears on surface - - Caused by twinning interference + - Caused by Bøggild exsolution lamellae interference - Plagioclase feldspar - title: Cutting for Adularescence diff --git a/docs/learn/phenomena/labradorescence.yaml b/docs/learn/phenomena/labradorescence.yaml index 05b7a49..83b9045 100644 --- a/docs/learn/phenomena/labradorescence.yaml +++ b/docs/learn/phenomena/labradorescence.yaml @@ -29,12 +29,17 @@ sections: content: | The cause of labradorescence: subsections: - - title: Lamellar Twinning + - title: Bøggild Exsolution Lamellae content: | - - Caused by light interference from repeated thin twin layers - - Twin lamellae form during cooling of plagioclase + - Caused by light interference from Bøggild exsolution lamellae + - The colour-causing structure is exsolution intergrowth of compositionally + distinct plagioclase end-members (within the Bøggild miscibility gap, + An ~ 47–58), not mechanical twinning. Lamellar thickness 100–300 nm + produces the spectral interference colours. - Lamellae vary in thickness, producing different colours - - Light interferes between twin boundaries + - Light interferes between exsolution layer boundaries + + Source: Gem-A D7 (labradorescence section); standard mineralogy references. - title: Orientation Dependence content: | @@ -102,7 +107,7 @@ sections: - Multiple spectral colours - Sharp, distinct flashes - Colours appear in patches - - Caused by lamellar twinning + - Caused by Bøggild exsolution lamellae - Plagioclase (labradorite) - Effect at surface level - title: Adularescence diff --git a/docs/learn/phenomena/play-of-colour.yaml b/docs/learn/phenomena/play-of-colour.yaml index db4dd00..22c171b 100644 --- a/docs/learn/phenomena/play-of-colour.yaml +++ b/docs/learn/phenomena/play-of-colour.yaml @@ -19,12 +19,15 @@ sections: content: | Play of colour is the flashing spectral colours seen in precious opal. It is opal's defining characteristic and distinguishes precious opal from common - opal (potch). The effect results from light diffraction by regularly arranged - silica spheres within the opal structure. + opal (potch). The effect results from Bragg-style diffraction and interference + by regularly stacked silica spheres (150–400 nm) within the opal structure. - Unlike interference effects (adularescence, labradorescence), play of colour - is a diffraction phenomenon, producing pure spectral colours that shift - with viewing angle. + Play of colour is caused by diffraction and interference — the regularly stacked + sphere array acts as a 3D diffraction grating, while constructive/destructive + interference between scattered rays selects the colours seen. Viewing-angle shifts + arise from the geometric change in effective path difference. + + Source: Gem-A D7 p. D7-32; Gem-A Gem Hub article on opal colour patterns. - title: Cause content: | @@ -150,14 +153,14 @@ sections: subsections: - title: Key Differences content: | - - **Play of colour** (opal): Diffraction; pure spectral colours + - **Play of colour** (opal): Diffraction and interference; spectral colours - **Labradorescence**: Interference; colours in patches - **Iridescence**: Thin-film; rainbow sequence - **Adularescence**: Interference; single colour glow - title: Physical Cause content: | - - Opal: 3D sphere array (diffraction) + - Opal: 3D sphere array (diffraction and interference) - Labradorite: Twin lamellae (interference) - Iridescent gems: Surface layers (interference) - Moonstone: Exsolution layers (interference) diff --git a/docs/learn/species/beryl.yaml b/docs/learn/species/beryl.yaml index a6536ed..7a71a65 100644 --- a/docs/learn/species/beryl.yaml +++ b/docs/learn/species/beryl.yaml @@ -44,8 +44,8 @@ sections: rows: - ["Hardness", "7.5-8 Mohs"] - ["Specific gravity", "2.67-2.78"] - - ["Refractive index", "1.577-1.583"] - - ["Birefringence", "0.005-0.009"] + - ["Refractive index", "1.560-1.600"] + - ["Birefringence", "0.003-0.010"] - ["Optic character", "Uniaxial negative"] - ["Pleochroism", "Weak to distinct (varies by variety)"] - ["Lustre", "Vitreous"] diff --git a/docs/learn/species/spinel.yaml b/docs/learn/species/spinel.yaml index 8ef22a7..9098930 100644 --- a/docs/learn/species/spinel.yaml +++ b/docs/learn/species/spinel.yaml @@ -43,7 +43,7 @@ sections: rows: - ["Hardness", "8 Mohs"] - ["Specific gravity", "3.58-3.61"] - - ["Refractive index", "1.712-1.720"] + - ["Refractive index", "1.712-1.740"] - ["Optic character", "Singly refractive (isotropic)"] - ["Pleochroism", "None"] - ["Dispersion", "0.020 (moderate)"]