Key properties
| Chemical formula | ZrSiO4 |
| Crystal system | Tetragonal |
| Mohs hardness | 6-7.5 |
| Toughness | Fair to good in untreated stones; poor to fair in heat-treated material |
| Refractive index | 1.780-1.984 |
| Birefringence | 0.0000-0.0590 |
| Optic character | Uniaxial positive (low/metamict types may appear virtually singly refractive) (+) |
| Dispersion | 0.0380 |
| Specific gravity | 3.90-4.73 |
| Cleavage | None (poor prismatic cleavage, not seen in cut stones) |
| Fracture | Conchoidal |
| Habit | Prismatic tetragonal crystals, often as rounded waterworn pebbles in alluvial gem gravels |
| Lustre | Vitreous to subadamantine; polish: Adamantine to vitreous |
| UV fluorescence | Variable: some yellow, orange and red stones glow yellow to orange (best in short-wave); some blue stones weak light blue in long-wave; many stones inert |
| Pleochroism | None to strong depending on colour: blue stones show strong blue against brownish yellow to near colourless; reds show reddish purple against purplish brown; greens nearly none |
| Cause of colour | Colour centres produced by natural radioactive damage to the crystal lattice over geological time; zircon contains traces of uranium and thorium which break the structure down (metamict state), and the degree of this breakdown, plus heat treatment, controls RI, SG, birefringence and colour |
| Typical inclusions | Angular and skeletal inclusions • 'snowball' inclusions (broken-crystal clusters) • tension fractures and fingerprints • strong repeated twinning and zoning in low-type greens, sometimes giving a cloudy or milky look • minute white cottony wisps in some blue and colourless stones |
| Stability | Generally stable to light and chemicals • some heat-treated stones slowly revert toward their original brown • moderate heat is tolerated but a jeweller's torch can damage or decolour a stone |
| Heat sensitivity | Variable - torch work during repair is risky; sudden temperature change can crack the brittle material |
| Care and cleaning | Warm soapy water safe • avoid ultrasonic and steam cleaners, especially for heat-treated stones • set in protective mounts and avoid rough wear which abrades facet edges |
| Birthstones | December (modern list), sharing the month with tanzanite and turquoise |
| Availability | Limited - fine blue and red material is sporadic; brown and green more available but still modest supply |
| Recognition | High adamantine lustre with strong fire • obvious doubling of facet junctions and inclusions in high-type stones (large birefringence) • hand spectroscope line at 653.5 nm (often with companions) is close to diagnostic • RI usually over the refractometer limit, spot readings around 1.92-1.98 for high type |
Varieties (6)
Red Zircon (Hyacinth)
| Colour | brownish red to orangy red and reddish brown |
| Transparency | transparent |
| Clarity type | Type II - usually eye-clean |
| Phenomena | Chatoyancy very rare |
| Appearance | Warm glowing red-brown with adamantine sparkle and visible doubling, often with slight silkiness from inclusions |
| Trade names | Hyacinth (jacinth) - reddish brown transparent zircon, historically also applied to hessonite garnet |
| Misnomers | Hyacinth has been used for hessonite garnet too - always confirm species |
| Typical sizes | Usually under 3 ct; faceted stones over 10 ct are rare |
| Cutting styles | Faceted; the traditional 'zircon cut' is a round brilliant with an extra tier of facets around the culet to save brittle material |
| Key separations | Vs hessonite garnet: garnet is singly refractive with no doubling, RI about 1.745, roiled granular inclusions • Vs spessartite garnet: singly refractive, different spectrum (Mn bands at 430/460/500) • Vs fire opal: much lower SG (about 2.0) and hardness • Spectrum 653.5 nm line confirms zircon |
| Sources (localities) | Sri Lanka (classic hyacinth) • Cambodia • Myanmar • Tanzania • Thailand • Australia |
| Availability | Limited; fine red is scarce |
| Market notes | Untreated natural colour; price sits between fine blue zircon and common brown |
| Care notes | Protect from knocks; ultrasonic risky; warm soapy water only |
| In short | Red to reddish-brown zircon, the historic hyacinth, is high-type material with strong doubling and diamond-like fire. Stones are small and supply modest, mainly from Sri Lanka and Southeast Asia. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–3.00 | $40.00 – $200.00 | 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.
Blue Zircon (Starlite)
| Colour | very strongly greenish blue through green-blue, sometimes with a steely cast |
| Transparency | transparent |
| Clarity type | Type I - normally eye-clean |
| Phenomena | None routinely; chatoyancy very rare |
| Appearance | Bright steel to sky blue with exceptional adamantine lustre and fire; the doubling of back-facet edges gives a sleepy depth |
| Trade names | Starlite (historic marketing name for fine blue zircon) • Stremlite |
| Misnomers | 'Siam aquamarine' historically used for blue zircon - it is not aquamarine |
| Typical sizes | 1 to 9 ct typical; giants over 20 ct occasionally seen |
| Cutting styles | Faceted; zircon cut and modern brilliants; avoid delicate culets in exposed settings |
| Key separations | Vs blue sapphire: sapphire RI 1.76-1.77, moderate doubling, different inclusions; zircon reads above the RI limit and doubles strongly • Vs blue topaz: topaz RI 1.62, SG 3.53, weaker fire • Vs tanzanite: tanzanite RI 1.69, strong pleochroism, hardness 6.5 • 653.5 nm line and SG about 4.65 confirm zircon |
| Sources (localities) | Cambodia (Ratanakiri - the heat-treatment rough) • Sri Lanka • Myanmar • Thailand • Vietnam • Australia |
| Availability | Limited but the best-known zircon colour in the trade |
| Market notes | Virtually all blue zircon is heat treated from brown rough and must be disclosed; prices peak for saturated even blue in 3-10 ct clean stones |
| Care notes | No ultrasonic or steam; warm soapy water only; protective settings advised since abraded facet junctions show quickly |
| In short | Blue zircon, sold historically as starlite, is made by heat-treating brown Cambodian rough. It is the most prized zircon colour, combining sky-to-steel blue with remarkable fire and obvious doubling. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–5.00 | $30.00 – $150.00 | commercial to fine | 2026-10-26 |
| 5.00–10.00 | $100.00 – $400.00 | 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.
Green Zircon
| Colour | yellowish green to brownish green, often cloudy or zoned |
| Transparency | transparent |
| Clarity type | Type II - visible zoning and twinning common |
| Phenomena | None |
| Appearance | Soft brownish to yellowish green with a cloudy, sleepy look; strong repeated twinning or banding often visible to the naked eye |
| Trade names | Beccarite (green zircon, archaic) |
| Typical sizes | 1 to 9 ct common; large low-type stones known |
| Cutting styles | Faceted; also step cuts to show even colour |
| Key separations | Dense diagnostic absorption: greens may show dozens of lines and bands across the spectrum with the 653.5 nm line family prominent • Vs peridot: peridot RI 1.65-1.69, SG 3.34, lily-pad inclusions • Vs green sapphire: lower RI and no doubling in the zircon • The very strong twinning/zoning and near-SR optic character mark low-type zircon |
| Sources (localities) | Cambodia and Sri Lanka low-type rough • Myanmar • Tanzania • Australia |
| Availability | Modest; mainly collector and alternative-jewellery demand |
| Market notes | Cheapest zircon colour; sold as natural untreated - true, since heating low-type green usually fails or dulls the stone |
| Care notes | Softer and more brittle than high type - avoid ultrasonic, wear gently |
| In short | Green zircon is the low-type, metamict member of the family, with RI near 1.81, weak birefringence, cloudy texture and a spectacular crowded absorption spectrum. It is the classic teaching stone for radiation-damage effects. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–9.00 | $10.00 – $60.00 | commercial to collector | 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.
Yellow-Orange Zircon
| Colour | golden yellow to honey orange and orange-brown |
| Transparency | transparent |
| Clarity type | Type II - usually eye-clean |
| Phenomena | Chatoyancy very rare |
| Appearance | Rich honey-gold with sparkling adamantine fire, often slightly sleepy from doubling |
| Trade names | Jargoon (jargon) - pale to colourless Sri Lankan stones, loosely applied to yellowish material • Melichrysos (yellow, archaic) |
| Misnomers | Fine yellow zircon occasionally misrepresented as 'hyacinth topaz' or simply 'topaz' in older jewellery |
| Typical sizes | 1 to 4 ct typical; larger stones rare |
| Cutting styles | Faceted brilliants and zircon cuts |
| Key separations | Vs yellow sapphire: sapphire on-scale RI 1.76-1.77, no strong doubling • Vs citrine: quartz RI 1.544-1.553, much lower lustre and fire • Vs spessartite garnet: singly refractive, RI about 1.81, manganese spectrum • 653.5 nm line plus SG about 4.6 identify zircon |
| Sources (localities) | Cambodia • Sri Lanka • Myanmar • Thailand • Vietnam • Tanzania |
| Availability | Limited |
| Market notes | Popular alternative to yellow sapphire at a fraction of the price; most is heat treated |
| Care notes | No ultrasonic or steam; gentle wear |
| In short | Golden to orange zircon delivers honey warmth with exceptional fire, nearly always via heat treatment of brown rough. Strong doubling and high SG separate it instantly from yellow sapphire or citrine. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–4.00 | $20.00 – $120.00 | 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.
Colourless Zircon
| Colour | water-clear colourless |
| Transparency | transparent |
| Clarity type | Type I - normally eye-clean |
| Phenomena | Chatoyancy very rare |
| Appearance | Bright, fiery near-diamond look with adamantine lustre; white cottony wisps common under magnification |
| Trade names | Matura diamond (Matara diamond, after the Sri Lankan district) • Jargoon (jargon) • Sparklite |
| Misnomers | 'Matura diamond' and 'Ceylon diamond' - it is zircon, not diamond |
| Typical sizes | 1 to 9 ct typical; museum cuts over 100 ct exist |
| Cutting styles | Faceted; brilliant and zircon cuts |
| Key separations | Vs diamond: diamond is singly refractive with no doubling, superior hardness 10, thermal probe reads diamond • Vs CZ: CZ singly refractive RI about 2.15-2.18, SG about 5.8, usually flawless • Vs strontium titanate and synthetic rutile: far higher dispersion, much lower hardness • Vs YAG/GGG: singly refractive, different SG • The 653.5 nm line and SG about 4.6-4.7 confirm zircon |
| Sources (localities) | Cambodia (heated) • Sri Lanka (classic Matura stones) • Myanmar • Thailand • Australia |
| Availability | Limited; niche demand as an honest natural diamond look-alike |
| Market notes | Nearly all colourless zircon is heat treated and must be disclosed; sells as an affordable natural alternative to diamond with genuine fire |
| Care notes | No ultrasonic or steam; protective settings; facet edges abrade with rough wear |
| In short | Colourless zircon, the old 'Matura diamond', is heat-treated high-type material whose fire and adamantine lustre made it the diamond substitute of earlier centuries. Doubling, SG and the 653.5 nm line separate it from every simulant. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–5.00 | $20.00 – $100.00 | 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.
Dark Zircon
| Colour | dark brown to coffee brown, sometimes nearly black |
| Transparency | transparent |
| Clarity type | Type II |
| Phenomena | Chatoyancy very rare |
| Appearance | Deep coffee brown with warm adamantine sparkle; stones can look like dark sherry or smoked topaz |
| Trade names | Brown zircon is the starting rough for virtually all treated blue and colourless stones |
| Misnomers | 'Smoky topaz' mislabel - smoky quartz and topaz are different minerals |
| Typical sizes | 1 to 9 ct typical; giants over 100 ct known |
| Cutting styles | Faceted brilliants; also beads in ethnic jewellery |
| Key separations | Vs smoky quartz: quartz RI 1.544-1.553, SG 2.65, weak fire • Vs brown tourmaline: RI 1.62-1.64, strongly pleochroic, different SG • Vs brown garnet: singly refractive • Spectrum and high SG settle it |
| Sources (localities) | Cambodia • Sri Lanka • Myanmar • Thailand • Vietnam • Australia • Tanzania |
| Availability | The most available zircon colour |
| Market notes | Modest prices; much of the annual Cambodian production is bought specifically as treatment rough |
| Care notes | No ultrasonic or steam; warm soapy water |
| In short | Dark brown is zircon's natural colour and the feedstock for the treated blue and colourless market. Untreated, it is an affordable, fiery brown gem whose constants vary with its metamict state. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–9.00 | $8.00 – $50.00 | commercial | 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 #2 · gem #39 · gem #65 · gem #102 · gem #159 · gem #196
Related materials: Corundum · Diamond · Opal · Quartz · Spinel · Topaz
Identification wizard · All 83 materials · Singapore gem labs