Key properties
| Chemical formula | SiO2 |
| Crystal system | Trigonal |
| Mohs hardness | 7 |
| Toughness | Good |
| Refractive index | 1.544-1.553 |
| Birefringence | 0.0090 |
| Optic character | DR (doubly refractive), uniaxial positive; massive varieties show aggregate (AGG) reaction (+) |
| Dispersion | 0.0130 |
| Specific gravity | 2.64-2.69 |
| Cleavage | None |
| Fracture | Conchoidal (uneven to granular in aggregates) |
| Habit | Prismatic hexagonal crystals, often terminated; translucent to opaque varieties massive (microcrystalline quartz belongs to chalcedony) |
| Lustre | Vitreous; polish: Vitreous |
| UV fluorescence | Generally inert; some varieties fluoresce weakly (see each variety) |
| Pleochroism | None to weak depending on variety and depth of colour (see each variety) |
| Cause of colour | Colour centres and trace impurities: iron centres for amethyst and citrine, aluminium centres activated by irradiation for smoky quartz, nanoscale mineral inclusions for rose quartz and aventurine; pure quartz is colourless rock crystal |
| Typical inclusions | Liquid, two-phase and three-phase inclusions • negative crystals • colour zoning • Brazil-law twinning (bull's-eye optic figure) • needles of rutile/tourmaline/actinolite in sagenitic types |
| Stability | Stable to light and normal chemicals; soluble in hydrofluoric acid and ammonium fluoride; very slightly soluble in alkalis |
| Heat sensitivity | Sudden temperature change can fracture any quartz; strong heat alters or destroys the colour of most varieties |
| Care and cleaning | Ultrasonic usually safe • steamer risky • warm soapy water safe |
| Birthstones | Species-level none; amethyst is February's birthstone and citrine November's (see varieties) |
| Availability | Plentiful to scarce depending on variety; quartz is the most abundant mineral in the earth's crust |
| Recognition | Rock crystal, amethyst, citrine and smoky quartz are household names; the rarer varieties (prasiolite, ametrine) are niche |
Varieties (11)
Amethyst
| Colour | bluish purple to purple to reddish purple; often shifts hue between daylight and incandescent light |
| Transparency | transparent |
| Clarity type | Type II - typically included; eye-clean material easy to source |
| Phenomena | None (rare cat's-eye and star amethyst exist) |
| Appearance | Purple from delicate lilac to deep royal violet; the best stones stay saturated without darkening to ink, and colour zoning in bands parallel to rhombohedral faces is common. |
| Trade names | Deep Siberian / Siberian (top purple with red and blue flashes) • Rose de France (pale lilac) • Uralian or Siberian amethyst (historic fine grades) • Uruguay amethyst (market grade for deeptone material) |
| Misnomers | 'Oriental amethyst' (historic, for purple sapphire) |
| Typical sizes | 1-20 ct standard; giant faceted stones over 1000 ct exist |
| Cutting styles | Faceted in every shape; also beads, cabochons, carvings; geode slices for decoration |
| Key separations | vs iolite: iolite strong trichroism (colourless/yellow/blue), lower RI (~1.53-1.55 across axes), distinct cleavage • vs purple scapolite: scapolite optic sign negative, cleavage present • vs fluorite: fluorite SR, RI 1.434, perfect octahedral cleavage, much softer (4) • vs synthetic amethyst: identical constants - check twinning pattern under crossed polars (Brazil-law twinning in natural) and inclusions; colour zoning parallel to z-axes suggests natural |
| Sources (localities) | Brazil (Rio Grande do Sul, Bahia, Minas Gerais) • Uruguay (Artigas) • Zambia (Kalomo) • Bolivia • Madagascar • Morocco • Namibia (Brandberg) • Russia (historic Siberian) • Canada (Thunder Bay) • USA (Four Peaks, Arizona) |
| Availability | Plentiful; fine deep Siberian colour always in demand |
| Market notes | Once a cardinal gem as valuable as ruby and sapphire until Brazilian deposits flooded the 19th-century market. Synthetic (hydrothermal) amethyst is widespread and cheap; buy from reliable sources when colour and natural origin matter. |
| Care notes | Some stones fade with prolonged strong light; avoid heat - turns colourless, yellow (citrine) or green |
| In short | Amethyst is the purple iron-coloured quartz and February's birthstone, from pale lilac Rose de France to deep Siberian violet. Affordable, abundant and available in every size, it is the most worn purple gem. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–5.00 | $5.00 – $60.00 | commercial to fine | 2026-10-26 |
| 5.00–20.00 | $8.00 – $100.00 | fine to top Siberian colour | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Ametrine
| Colour | bicolour - purple amethyst zones alternating with yellow-orange citrine zones |
| Transparency | transparent |
| Clarity type | Type II - typically included |
| Phenomena | None |
| Appearance | Half purple, half golden in one gem - cutters orient the colour boundary along the table so both colours flash in one stone. |
| Trade names | bolivianite • trystine • golden amethyst |
| Misnomers | none current |
| Typical sizes | 1-20 ct common; larger clean stones available from Anahi rough |
| Cutting styles | Emerald cuts and step cuts with the colour boundary on the table; fancy cuts that fold the boundary for chevron patterns |
| Key separations | vs assembled doublet (glass-glass or quartz-quartz glued): look for flat colour boundary at a glue plane, bubbles in the join • vs synthetic ametrine: unnatural green-yellow or golden-blue combinations never occur naturally; check twinning and seed plate in hydrothermal synthetics • vs bicolour tourmaline: tourmaline different RI (1.62-1.64), striated prisms, stronger pleochroism |
| Sources (localities) | Bolivia (Anahi mine, near the Brazil border - effectively the only commercial source) • minor: Brazil, India |
| Availability | Steady but single-mine dependent; any size and shape cut from Anahi rough |
| Market notes | Legend traces the mine to a Spanish conquistador's dowry in the 1600s. Hydrothermal synthetic ametrine is commercially grown and should always be disclosed; greenish-yellow 'ametrine' colours betray it. |
| Care notes | As quartz: no steamers, guard against knocks on the bench |
| In short | Ametrine is the two-in-one quartz - amethyst purple and citrine gold in a single crystal - mined almost exclusively at Bolivia's Anahi mine. Skilful cutting puts both colours on display. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–5.00 | $10.00 – $60.00 | commercial to fine | 2026-10-26 |
| 5.00–15.00 | $20.00 – $120.00 | fine well-split colour | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Citrine
| Colour | yellow through orange to reddish brown ('madeira') |
| Transparency | transparent |
| Clarity type | Type I - usually eye-clean |
| Phenomena | None |
| Appearance | Sunny yellow to burnt-orange gold; the best stones glow like honey with no brownish smear. |
| Trade names | madeira (deep orange-red, after the wine) • palmeira (bright orange from heated amethyst, trade term) |
| Misnomers | 'topaz' or 'smoky topaz' misused by tourist sellers for citrine and smoky quartz; 'gold topaz' |
| Typical sizes | 1-20 ct standard; very large stones common |
| Cutting styles | Faceted in all shapes, large cocktail sizes especially |
| Key separations | vs topaz: topaz RI 1.61-1.64, DR ~0.008-0.010, distinct basal cleavage, higher SG (3.53) • vs yellow beryl: beryl RI 1.57-1.58, DR 0.005-0.009, low SG 2.7 • vs yellow orthoclase/labradorite/scapolite: check RI, optic figure, cleavage • vs synthetic citrine: same twinning and inclusion logic as amethyst • vs amber: amber SG ~1.08 floats in saltwater, hot-point reaction |
| Sources (localities) | Brazil (Rio Grande do Sul and Minas Gerais - most material) • Bolivia • Spain • Madagascar • Uruguay • Russia (natural) • USA (natural, minor) |
| Availability | Plentiful - natural citrine is rare but heated amethyst supplies the whole market |
| Market notes | Practically all commercial citrine is heat-treated amethyst or smoky quartz; disclose when known. The paler 'lemon' end overlaps lemon quartz in the market. |
| Care notes | Stable colour once heated; standard quartz care |
| In short | Citrine is the golden quartz of November birthdays, almost always produced by heating amethyst. Bright, clean and inexpensive in every size, it rivals topaz for affordable warmth. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–10.00 | $5.00 – $40.00 | commercial to fine madeira | 2026-10-26 |
| 10.00–30.00 | $5.00 – $30.00 | large cocktail sizes | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Rose Quartz
| Colour | translucent pink, often very light in tone, to deeper rose |
| Transparency | translucent |
| Clarity type | N/A - translucent massive material |
| Phenomena | Asterism in star rose quartz (six-rayed, from aligned fibres) |
| Appearance | Soft cloudy pink with a greasy glow; massive material never approaches transparency but takes a delicious polish. |
| Trade names | star rose quartz (asteriated cabochons) |
| Misnomers | 'Bohemian ruby' (historic, for rose quartz beads) |
| Typical sizes | Any size from beads to large carvings; transparent crystal 'pink quartz' is a rare collector item |
| Cutting styles | Beads (the classic use) • cabochons including star cabs • carvings • spheres |
| Key separations | vs pink glass/quartzite: fracture surface, SG, inclusions • vs pink chalcedony: chalcedony waxy translucency, lower SG spot readings • vs kunzite: kunzite transparent, strong pleochroism, RI 1.66-1.68 • dyed material: colour in cracks |
| Sources (localities) | Brazil (Minas Gerais - main) • Madagascar • Mozambique • Namibia • India • Sri Lanka • USA (South Dakota, Maine - rare euhedral crystals) |
| Availability | Plentiful as rough and beads |
| Market notes | Bead bracelets and spheres dominate. The rare transparent pink quartz crystals (Maine, Brazil) fade with light exposure and are collector stones - different mechanism from massive rose quartz, which is stable. |
| Care notes | Colour generally stable; keep the rare crystal 'pink quartz' out of strong light |
| In short | Rose quartz is the massive pink quartz of beads, spheres and carvings, coloured by tiny dumortierite-related fibres. Affordable and romantic, it is the staple pink ornamental stone. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–20.00 | $1.00 – $12.00 | ornamental | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Aventurine Quartz
| Colour | green (most common) plus grey, yellow-brown, orange and blue varieties |
| Transparency | opaque |
| Clarity type | N/A - translucent to opaque quartzite |
| Phenomena | Aventurescence - glittery reflections from tiny included platelets |
| Appearance | A granular green quartzite that throws golden-green sparkles when tilted; the mica flakes give depth that dye cannot imitate. |
| Trade names | green aventurine (fuchsite type) • goldstone is the glass imitation, not quartz |
| Misnomers | Indian jade (green aventurine) • 'Regalite' and similar marketing names for dyed quartzite sold as aventurine |
| Typical sizes | Abundant in all sizes; bangles, beads, cabochons |
| Cutting styles | Cabochons • beads • bangles • carvings |
| Key separations | vs jadeite/nephrite: jade's fibrous interlocking texture and SG; aventurine granular fracture • vs chrysoprase: chrysoprase colour in the chalcedony itself, no glittering flakes • vs aventurine feldspar (sunstone): feldspar lower hardness (6-6.5), cleavage, different RI • vs goldstone (glass): copper flakes, perfectly uniform sparkle, bubbles |
| Sources (localities) | India (major green) • Brazil (Bahia/Minas) • Russia • Chile (grey-white-orange types) • Spain • Austria • Tanzania |
| Availability | Plentiful and cheap |
| Market notes | A staple of craft jewellery and mala beads. Some deep-green material on the market is dyed quartzite rather than fuchsite aventurine. |
| Care notes | Wipe clean; mild soap; avoid ultrasonic for bangles with internal cracks |
| In short | Aventurine is a glittery quartzite whose mica or iron-oxide platelets create aventurescence. Green Indian material dominates the bead and cabochon trade at rock-bottom prices. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–30.00 | $0.50 – $8.00 | ornamental | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Tiger's Eye Quartz
| Colour | brownish yellow to brown to reddish brown with wavy chatoyancy; hawk's-eye is greyish blue |
| Transparency | opaque |
| Clarity type | N/A - semitranslucent to opaque |
| Phenomena | Chatoyancy (cat's-eye) - wavy, silky band across the dome |
| Appearance | Golden brown silk with a travelling eye of light; the parallel fibre bundles shimmer like velvet as the stone moves. |
| Trade names | hawk's-eye / falcon's-eye (blue unoxidised) • zebra tiger's-eye (brown and blue striped) • tiger iron (banded with red jasper and hematite, Australia) • marra mamba (golden-blue Australian variety) |
| Misnomers | 'crocidolite' used loosely for the material (it is the replaced mineral); petrified wood mislabelled as tiger's-eye in tourist markets |
| Typical sizes | Boulder sizes available; any cabochon size common |
| Cutting styles | Cabochons oriented across the fibres • beads • cameos/intaglios • carvings |
| Key separations | vs banded chalcedony: appearance, fracture, spot RI • vs labradorite: labradorite labradorescence and cleavage, twinning • vs cat's-eye chrysoberyl: chrysoberyl RI 1.74-1.75, SG 3.7, much sharper eye, higher hardness • vs fibre-optic glass imitation: perfectly uniform eye and bright colours (pink, blue 'tiger iron' imitations) |
| Sources (localities) | South Africa (Griqualand West, Northern Cape - classic) • Australia (Pilbara tiger iron) • India • Sri Lanka • Namibia • China • USA • Brazil • Myanmar • Spain |
| Availability | Plentiful and inexpensive |
| Market notes | Blue hawk's-eye and red (heat-treated) material are standard trade goods; fibre-optic glass imitations are widespread in cheap jewellery. Cutting and grinding dry tiger's-eye can release amphibole fibre dust - cutters should wet-cut with extraction. |
| Care notes | Warm soapy water; avoid harsh acids used to lighten colour |
| In short | Tiger's-eye is chatoyant quartz formed when silica locked around crocidolite asbestos fibres, stained golden by iron oxide. South African material supplies the world with this affordable, silky, ever-popular cabochon stone. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–20.00 | $0.50 – $6.00 | ornamental | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Green Quartz (Prasiolite)
| Colour | transparent light to medium green to yellowish green |
| Transparency | transparent |
| Clarity type | Type I - usually eye-clean |
| Phenomena | None |
| Appearance | A soft leek to mint green, transparent and even - cooler and less saturated than emerald or chrome tourmaline. |
| Trade names | prasiolite (also misspelt praseolite in the trade) • 'greened amethyst' • vermarine (marketing) |
| Misnomers | green amethyst - banned or discouraged by most trade bodies because amethyst by definition is purple |
| Typical sizes | 1-15 ct common in clean material |
| Cutting styles | Faceted in all shapes; also beads and carvings |
| Key separations | vs green tourmaline: tourmaline RI 1.62-1.64, strong dichroism, striated prism crystals • vs peridot: peridot RI 1.65-1.69, olive hue, lily-pad inclusions • vs emerald: emerald RI 1.577-1.583, Type III clarity, diagnostics (jardin) • vs green glass: bubbles, SR |
| Sources (localities) | Brazil (Montezuma, Minas Gerais - natural and heated) • Poland (Różana, natural, minor) • also produced wherever suitable amethyst is heat-treated, e.g. Uruguay and Arizona material |
| Availability | Steady but modest; a niche transparent green at friendly prices |
| Market notes | Since 2006 most prasiolite is heated Brazilian amethyst; natural green quartz is a rare collector curiosity. Some material is additionally irradiated to reach green after heating - complex treatment chains should be disclosed. |
| Care notes | Colour can shift with prolonged strong heat; normal wear safe |
| In short | Prasiolite is transparent green quartz, almost always created by heating the right amethyst. It fills the demand for an affordable, clean, leek-green gem. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–10.00 | $8.00 – $50.00 | commercial to fine | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Milky Quartz
| Colour | white to very light grey, sometimes with a bluish cast |
| Transparency | translucent |
| Clarity type | N/A - translucent |
| Phenomena | Occasional sheen or cat's-eye effects; 'gold quartz' contains native gold |
| Appearance | Snowy, clouded white quartz - humble but attractive in beads and carvings, and often found as milky phantoms inside rock crystal. |
| Trade names | gold quartz (milky quartz with native gold inclusions) |
| Misnomers | 'moonstone' sold to tourists for milky quartz (true moonstone is feldspar) |
| Typical sizes | All sizes, carving rough abundant |
| Cutting styles | Beads • cabochons • carvings • spheres |
| Key separations | vs moonstone: moonstone feldspar (RI ~1.52-1.53, SG ~2.6 lower, cleavage, adularescence) • vs white chalcedony: chalcedony waxy translucency, no milky cloud, different fracture • vs white glass/plastic: bubbles, hardness test |
| Sources (localities) | Worldwide - Brazil, Alps, Arkansas (USA), Madagascar, China |
| Availability | Plentiful and very cheap |
| Market notes | Mostly decorative; 'gold quartz' from California historic mines is a collectible niche. |
| Care notes | Warm soapy water |
| In short | Milky quartz is clouded white quartz whose countless micro-inclusions scatter light. Beads, carvings and specimen bases keep it in steady ornamental use. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–30.00 | $0.50 – $8.00 | ornamental | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Lemon Quartz
| Colour | bright lemon yellow to yellowish green |
| Transparency | transparent |
| Clarity type | Type I - usually eye-clean |
| Phenomena | None |
| Appearance | A zesty yellow-green glow - livelier and greener than citrine, often in large clean calibrated gems. |
| Trade names | Ouro Verde (greenish-yellow irradiated/heated type) • lemon citrine (loose overlap) |
| Misnomers | 'green gold' marketing names |
| Typical sizes | Large clean stones easily found, 5-30 ct |
| Cutting styles | Faceted; large emerald cuts and trillions show the neon colour best |
| Key separations | vs citrine: citrine orange-gold; lemon quartz is greener - both share quartz constants, difference is colour/trade naming • vs heliodor: beryl RI 1.57-1.58, SG 2.72 • vs yellow glass: bubbles, SR |
| Sources (localities) | Brazil (Minas Gerais - essentially all commercial material) |
| Availability | Steady in calibrated sizes |
| Market notes | A treated product - treat disclosure as for citrine and prasiolite. Popular in bold yellow cocktail jewellery. |
| Care notes | Standard quartz care |
| In short | Lemon quartz is the bright yellow-green treated quartz of large cocktail gems, produced by heating (and sometimes irradiating) Brazilian amethyst. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 3.00–20.00 | $5.00 – $40.00 | commercial to fine | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Rock Crystal
| Colour | colourless, water-clear |
| Transparency | transparent |
| Clarity type | Type I - eye-clean material expected; included crystals sold as rutilated/tourmalinated quartz |
| Phenomena | Iridescence in crackled 'iris/rainbow' quartz; rutile/tourmaline needles in sagenitic types |
| Appearance | Perfectly colourless and limpid - the purest quartz, used since antiquity for vessels, spheres and crystal carvings. |
| Trade names | rutilated quartz (golden needles) • tourmalinated quartz (black needles) • iris/rainbow quartz (quench-crackled iridescent fractures) • Herkimer diamond (doubly-terminated New York crystals) |
| Misnomers | Herkimer diamond • Arizona/Arkansas/Alaska diamond • Cornish diamond - all rock crystal |
| Typical sizes | Any size including museum carvings and giant spheres |
| Cutting styles | Faceted • carved vessels and spheres • beads; rhinestones imitate it in glass |
| Key separations | vs colourless glass (rhinestone): glass SR, bubbles, lower durability • vs CZ/YAG/GGG: much higher SGs and RIs over limit • vs colourless zircon: zircon RI 1.92-1.98 high, strong DR • vs colourless sapphire: sapphire RI 1.762-1.777, DR, higher SG • vs diamond: diamond RI 2.417, adamantine, sharp facet junctions |
| Sources (localities) | Brazil (Minas Gerais/Corinto) • Madagascar • USA (Arkansas Hot Springs; Herkimer NY) • Alps (Switzerland) • China • Russia |
| Availability | Plentiful in all sizes |
| Market notes | The rhinestone (originally rock crystal from the Rhine) became the generic name for glass imitations - the original still outclasses paste in coolness and lustre. Coated 'aura' quartzes are sold with disclosure. |
| Care notes | Standard quartz care |
| In short | Rock crystal is pure colourless quartz - water-clear, abundant and historic, from crystal skulls to modern carved beads. It is the reference gem for quartz optics. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–20.00 | $2.00 – $20.00 | commercial to fine clean | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Smoky Quartz
| Colour | light brownish grey through dark brown to nearly black (morion) |
| Transparency | transparent |
| Clarity type | Type I - eye-clean expected; large clean stones common |
| Phenomena | Rare cat's-eye and star smoky quartz |
| Appearance | Warm brown smoke, from café-au-lait to near-black morion - autumnal and unisex, with excellent clarity in big sizes. |
| Trade names | cairngorm (Scottish mountain variety, whisky-coloured) • morion (near-black) • whisky quartz (marketing) |
| Misnomers | smoky topaz • Scotch topaz • burnt topaz - smoky quartz sold using topaz's name (illegal in most markets) |
| Typical sizes | Very large clean stones common (10-50 ct+) |
| Cutting styles | Faceted emerald cuts, cushions; carvings; beads |
| Key separations | vs smoky topaz: topaz RI 1.61-1.64, SG 3.53, hardness 8, basal cleavage • vs brown tourmaline: tourmaline RI 1.62-1.64, striated prisms, stronger pleochroism • vs andalusite: andalusite strong trichroism (yellow/green/red-brown), near-DG optics • vs glass: bubbles, SR |
| Sources (localities) | Brazil (Minas Gerais) • Switzerland (Alps) • Scotland (Cairngorms, historic) • USA (Colorado Pikes Peak, New Mexico) • Spain (Cordoba) • Mozambique • Madagascar • Ukraine/Russia |
| Availability | Plentiful |
| Market notes | Persistently confused with topaz by the public - the 'smoky topaz' label survives in tourist shops and should always be corrected. Much commercial dark material is irradiated to deepen colour. |
| Care notes | Colour can lighten with prolonged heat or strong light in some stones |
| In short | Smoky quartz is the brown irradiated quartz of cairngorm brooches and modern unisex jewellery - big, clean and inexpensive. It must be sold under its own name, never as 'smoky topaz'. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 3.00–20.00 | $5.00 – $60.00 | commercial to fine | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Sources
GIA gem encyclopedia · mindat.org · Wikipedia
Data compiled and fact-checked against gemmological literature, October 2026 (JDMIS gem reference). Properties are ranges accepted in gemmological practice; individual stones vary.
See also
Gemstone reference entries: gem #16 · gem #17 · gem #29 · gem #49 · gem #57 · gem #78 · gem #93 · gem #117
Related materials: Chalcedony
Identification wizard · All 83 materials · Singapore gem labs