On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Mineral species · Natural; common industry optimization (verify with certificate)
Zircon
Also known asBlue Zircon · Starlite
A mineral species with the composition ZrSiO4, commonly heat-treated from brown to blue or colourless; the division into low, medium and high types relates to its heat-treatment state. This page compares how the major standards and institutions name it, what must be disclosed when selling it, whether it can be worn every day, how it is treated and identified, and which source each conclusion comes from.
Price, rarity and origin are outside the scope of this wiki.
What this page can answer
This page covers
- How Zircon forms and what gives its colourFormation setting, process and timescale; where its colour and optical effects come from, each finding graded and sourced
- How to identify ZirconHow far lab testing can go and whether a synthetic exists
- Treatments and enhancements of Zircon2 registered treatments: status, stability, how common they are and identification leads
- Caring for and wearing ZirconCleaning, heat, chemicals and light, as the cited sources give them; durability indicators and wearing advice
- Hardness and density of ZirconEach value with its source and check date
- Zircon in English, Chinese and Japanese; national standard namesNames in four languages, the GB/T standard name and the suggested listing name, names in national standards; and: Which of GIA, FTC, CIBJO and Gem-A have a name for it on record, and do those agree?
- Name origin and history of ZirconWhere the name comes from; how people have used it, with museum objects
- Listing and disclosing ZirconThe listing name to use; what must be disclosed before sale
- Standard clauses that define ZirconWhich clause defines it, each cross-checked
What we cannot conclude
- Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.
- Geographic origin, unless an origin report accompanies the item.
- Price, rarity or investment value: this wiki covers naming and disclosure only.
Material research: formation, causes and history
What authoritative sources say about how this material forms, what causes its colour and optical effects, where its name comes from and how people have used it. Each statement carries an evidence grade and its sources; it describes the material in general, not any specific piece.
How it forms
Zircon has the formula ZrSiO4 and is tetragonal; it may become metamict through the radioactivity of contained uranium and thorium. It forms widely as an accessory mineral in igneous and metamorphic rocks, can reach large crystal size in mafic pegmatites and carbonatites, and concentrates in sedimentary rocks and alluvial heavy-mineral sands. Zircon is one of the most powerful geochronometers: its U–Pb radiogenic clocks start at crystallization, it can record peak temperatures yet generally survives post-cooling history, and it is widely used to date the crystallization of its host rock or inclusions.
Scope: Covers the origin, composition and occurrence of zircon as an accessory mineral species in igneous and metamorphic rocks, including its use in U–Pb dating; does not address synthetic or imitation materials.
Sources Handbook of Mineralogy · G&G Spring 2019
Where it forms
Occurs as an accessory phase in igneous as well as metamorphic rocks
Sources Handbook of Mineralogy
Mafic pegmatites and carbonatites (where large crystals may form)
Sources Handbook of Mineralogy
Sedimentary rocks and alluvial heavy-mineral sands (placer concentration)
Sources Handbook of Mineralogy
How it forms, step by step
In magmas or metamorphic fluids, zirconium and silica combine to crystallize ZrSiO4 zircon, mostly as an accessory mineral in igneous and metamorphic rocks.
Sources Handbook of Mineralogy
At crystallization the zircon starts its U–Pb radiogenic clocks; radiation damage may later render it metamict.
Because of its chemical and physical durability, zircon survives weathering and transport and concentrates in sedimentary rocks and alluvial heavy-mineral sands.
Sources Handbook of Mineralogy
When trapped as an inclusion in a host mineral (e.g. sapphire), zircon's U–Pb age can constrain the timing of the host's crystallization.
Link to appearance
Zircon may be reddish brown, yellow, green, blue, grey or colourless, with a vitreous to adamantine luster (greasy when metamict) and very strong dispersion; its colours relate to trace elements and colour centres. A rare zircon shifts to greyish purple under cool LED light and green under warm light; only gems with sharp absorption bands show this colour-change behaviour, and it is probably tied to rare-earth or actinide elements.
Sources G&G Fall 2021
Timescale
The sources present zircon as a U–Pb geochronometer (clocks starting at crystallization) and report U–Pb ages of approximately 549 Ma for zircon inclusions in Sri Lankan sapphires.
Sources G&G Spring 2019
Supporting findings
Zircon is an accessory mineral in igneous and metamorphic rocks, can reach large crystal size in mafic pegmatites and carbonatites, and concentrates in sedimentary rocks and alluvial heavy-mineral sands.
Evidence grade BScope: Describes zircon's general occurrence; it does not infer the origin or locality of any sample.
Sources Handbook of Mineralogy
Zircon is one of the most powerful chronometers; its U–Pb clocks start at crystallization and can record peak temperatures while generally surviving post-cooling history.
Evidence grade AScope: Describes zircon's use and limitations as a U–Pb chronometer; it gives no age for any specific deposit.
U–Pb dating of zircon inclusions in Sri Lankan sapphires yielded ages of approximately 549 Ma, indicating the crystallization age of the host sapphire.
Evidence grade AScope: A dating result for specific samples; it does not extrapolate to zircon or sapphire from other localities.
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Asia
- Ratanakiri Province, CambodiaMajor source of fine heated blue zircon; brown to reddish brown rough is heated to blue
Sources Gems & Gemology Summer 2009
- Sri LankaProduced in the 1990s
Sources Gems & Gemology Winter 2000
- Muling, Heilongjiang, ChinaNot yet mined commercially; a promising gem zircon source
Sources Gems & Gemology Spring 2011
Oceania
- Harts Range, Northern Territory, AustraliaDescribed in 1989 as relatively underdeveloped
Sources Gems & Gemology Winter 1989 · Gems & Gemology Winter 2000
These are localities recorded by authoritative sources, not an origin finding for any individual piece. The CIBJO Gemstone Book (2022, §4.2.3) says a place of origin names where a gem was mined or harvested, is a matter of opinion, does not imply a level of quality, and that cutting, processing or exporting centres must not be used to imply origin. See how far testing can go on this page, the origin determination guide and the overview of recorded localities.
Causes of colour and optical effects
A rare colour-change response in zircon is confined to stones whose absorption bands are sharp, probably tied to rare-earth or actinide elements, and its spectrum displays a uranium-related pattern.
Evidence grade AScope: Describes the absorption mechanism of a specific colour-change zircon; not all zircons show colour change.
Sources G&G Fall 2021
Where the name comes from
Zircon's name is thought to derive, by way of Arabic zarqun, from the Persian zar ("gold") and gun ("colour").
Evidence grade BScope: This states only the origin of the name and does not establish the material's composition, locality, natural origin, or whether it was treated.
Sources Handbook of Mineralogy
Human use and museum objects
Only three collection objects are recorded as containing zircon (Met 15.95.173a, b amulet case; Met 32.75.35 and 32.75.42 watches), all objects rather than beadwork and none ancient; the evidence is sparse and cannot summarise zircon's general history of use.
Evidence grade AScope: Applies to the few collection objects labelled zircon/zircons; the evidence is sparse and is limited to the three cited objects, with no further inference drawn.
Sources The Met 15.95.173a, b · The Met 32.75.42 · The Met 32.75.35
Only three objects in the collection are explicitly recorded as containing zircon, and all are objects rather than beadwork, with no ancient instance: a 17th-19th century Nepalese amulet case (Met 15.95.173a, b) in which zircon is set alongside rubies, sapphires, emeralds, pearls, coral, lapis lazuli and turquoise; and two watches of ca. 1780 and 1800 (Met 32.75.35, 32.75.42) set with zircons. The evidence is sparse and cannot summarise the history of zircon's use; it is reported here only as the collection shows it.
Sources The Met 15.95.173a, b · The Met 32.75.42 · The Met 32.75.35
Scope: A museum object evidences only the existence and date of that artefact itself; it does not establish widespread ancient use of the material, nor does it attest the origin, naturalness, or treatment of any modern specimen.
Objects cited
- The Met 15.95.173a, bGold, rubies, sapphires, emeralds, pearls, zircon, coral, lapis lazuli, and turquoise
- The Met 32.75.42Gold, enamel, zircons, silver, steel
- The Met 32.75.35Gold, enamel, zircons
Cultural records for this material: Birthstone list.
Other research findings
Zircon has the formula ZrSiO4, is tetragonal, and may become metamict through radioactivity.
Evidence grade BScope: Describes zircon's composition and structure; not the degree of metamictization of any specimen.
Sources Handbook of Mineralogy
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The cited mineralogical source states no absolute age of zircon formation; the reported ~549 Ma applies only to zircon inclusions in Sri Lankan sapphires.
- The chromophores/colour centres for zircon's various colours are not systematically given by these sources; no chromophore attribution is made except for the colour-change zircon.
Methodology
- Origin determination and its limits
- Quality grading and value factors
- How gemmology became a technical discipline
Evidence grades
- A
- Standards bodies, government geological surveys, peer-reviewed research and museum records
- B
- Institutional educational material
- C
- Specialist databases or cautious readings
A statement is never graded above its strongest source.
This section is LumaLark's own factual restatement of public authoritative sources, credited item by item; it contains no verbatim excerpts, images or third-party logos.
DecideListing name, disclosure, care and treatments
- Suggested listing name
- Zircon
GB/T 16552—2017 Table A.1 “Zircon” · CIBJO Gemmological Laboratories Book 2024 §7.2.1.266 “Zircon”
Construction or treatment status
Natural; common industry optimization (verify with certificate)
Treatments recorded for this material: Heated / Heat-treated, Irradiated
Related:Disclosure and cautions
This page cannot answer
Natural? · Origin · Price
A lab report settles these; this wiki covers naming and disclosure.
Related:What this page can answer
Answer at a glance
Zircon is often subjected to heating. Under GB/T 16552-2017, heating counts as an optimization, so the plain gem name may be used (§5.4.2.1 a). Do not assume it is unenhanced.
What this means for you
Before buying, check the recommended listing name "Zircon" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.
Known uncertainty
- See “Disclosure and cautions” above
- Disclosure rules for the treatments above can change as authorities update their standards; re-check before relying on this page.
- Last reviewed
- 2026-09-01
Care and wear
Normal care for every gemstone (CIBJO Gemstone Book §6.1), in brief:
- Handle it gently.
- Store pieces apart when not worn, so they cannot scratch each other.
- Clean with warm soapy water and a soft brush.
- Use ultrasonic cleaners only with caution.
The §6.1 wording and the full list of §6.2 special-care letters cited on this page are on the general gem care page.
Care
care (cleaning)3 sources compared
Zircon — care (cleaning): ultrasonic and steamer: relatively safe.
Gems & Gemology 1987 (Martin)
- Treatment state
- untreated
- Qualification
The rating comes from the durability chart in Gems & Gemology (Summer 1987) and covers untreated stones only; it contradicts GIA’s current care advice for zircon, and both are shown.
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zircon row, CLEANING column (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (cleaning): Warm soapy water is recommended; ultrasonic and steam cleaners are not.
GIA Gem Encyclopedia (care guide)
- Treatment state
- any treatment state
- Qualification
GIA’s care page is current consumer advice (September 2026 snapshot) and does not separate treated from untreated stones; it contradicts the 1987 durability chart’s rating for untreated zircon, and both are shown.
Source & check 2026-09-26
- Source
- GIA Gem Encyclopedia — Zircon Care and Cleaning Guide: Section “Cleaning” (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (cleaning): Some stones are susceptible to damage from ultrasonic cleaning. Do not expose them to ultrasonic cleaning.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code j
- Treatment state
- treated
- Only after these treatments
- heating
Source & check 2026-09-25
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Zircon, p.87; §6.2 j (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
How the sources relate
- Gems & Gemology 1987 (Martin) and GIA Gem Encyclopedia (care guide)
The two sources say opposite things.
GIA’s zircon care page recommends warm soapy water and advises against ultrasonic and steam cleaners without separating treated from untreated stones, while the durability chart in Gems & Gemology (Summer 1987) rates both ultrasonic and steam cleaning of untreated zircon as relatively safe.
The two overlap on untreated zircon and contradict each other there; both are shown as published, without a ruling from LumaLark.
Zircon — care (heat): Heat can alter the colour of some zircon; it is generally stable in light and to chemicals.
GIA Gem Encyclopedia (care guide)
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- GIA Gem Encyclopedia — Zircon Care and Cleaning Guide: Section “Stability” (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
care (light)2 sources compared
Zircon — care (light): Some heat-treated stones revert to their original colour (usually light brown) after long exposure to bright light.
GIA Gem Encyclopedia (care guide)
- Treatment state
- treated
- Only after these treatments
- heating
Source & check 2026-09-26
- Source
- GIA Gem Encyclopedia — Zircon Care and Cleaning Guide: Section “Stability” (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (light): may fade or revert to its original colour in strong light; do not wear or leave it in strong light for extended periods.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code f
- Treatment state
- treated
- Only after these treatments
- heating
Source & check 2026-09-25
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Zircon, p.87; §6.2 f (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
care (wear)2 sources compared
Zircon — care (wear): Mohs 6 to 7.5 with fair to good toughness; it can be brittle, so wear and store it where it will not rub hard against other materials.
GIA Gem Encyclopedia (care guide)
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- GIA Gem Encyclopedia — Zircon Care and Cleaning Guide: Section “Hardness and toughness” (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (wear): cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code b
- Treatment state
- treated
- Only after these treatments
- heating
Source & check 2026-09-25
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Zircon, p.87; §6.2 b (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
Zircon — care (special care): All heat-treated stones need special care (SC): yellow stones, avoid harsh abrasives; blue and colourless stones, avoid strong UV light; red and pink stones, avoid both.
AGTA Gemstone Information Manual, 17th ed.
- Treatment state
- treated
- Only after these treatments
- heating
Source & check 2026-09-26
- Source
- AGTA Gemstone Information Manual, 17th edition (August 2026) (AGTA): p.XVI, Gemstone Information Chart, Zircon Yellow H / Blue and Colorless H / Red H / Pink H, CARE REQUIRED / SPECIAL ADVICE (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (special care): untreated green and brown stones: special care (SC); avoid harsh abrasives.
AGTA Gemstone Information Manual, 17th ed.
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- AGTA Gemstone Information Manual, 17th edition (August 2026) (AGTA): p.XVI, Gemstone Information Chart, Zircon Green, Brown N, CARE REQUIRED / SPECIAL ADVICE (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (setting): prong, bezel and channel: use caution; flush and pavé: avoid; note: brittle and abrades easily.
Gems & Gemology 1987 (Martin)
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zircon row, SETTING column (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (repair): pickle pot and polishing: relatively safe; jeweller's torch and thermal shock: avoid; note: avoid heat, which may change the colour.
Gems & Gemology 1987 (Martin)
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zircon row, REPAIR column (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (display): artificial light: relatively safe; heat in the display case and sunlight: use caution.
Gems & Gemology 1987 (Martin)
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zircon row, DISPLAY column (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zircon — care (display): heated stones: some revert to their original colour in light.
Gems & Gemology 1987 (Martin)
- Treatment state
- treated
- Only after these treatments
- heating
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zircon row, DISPLAY column (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Common care questions and matching entries
CleaningCleaning Zircon: Martin, Gemstone Durability: Design to Display (Gems & Gemology, Summer 1987), covering only untreated Zircon, rates ultrasonic and steam cleaning as relatively safe; GIA, for any treatment state, recommends warm soapy water and advises against ultrasonic and steam cleaners; CIBJO, only for heat-treated Zircon, states that it must not be cleaned ultrasonically. Heat and chemicals: GIA, for any treatment state, states that heat can alter the colour of some Zircon and that it is stable to chemicals. Light: GIA, only for heat-treated Zircon, states that some stones may revert to their original colour, usually light brown, after prolonged exposure to strong light; CIBJO, only for heat-treated Zircon, states that it may fade or revert to its original colour in strong light, so it should not be worn or kept in strong light for long periods. Wear: GIA, for any treatment state, gives a Mohs hardness of 6–7.5 and fair to good toughness, notes that it may be brittle, and advises avoiding hard contact and rubbing against other materials when wearing and storing it.
This table scrolls sideways on narrow screens.
Care entries by treatment state
The same entries grouped by the treatment state each applies to; each links to its full wording and source. Letters are CIBJO special-care codes, explained on the gemstone care page.
untreated
- ultrasonic and steamer: relatively safe
- untreated green and brown stones: special care (SC); avoid harsh abrasives
- prong, bezel and channel: use caution; flush and pavé: avoid; note: brittle and abrades easily
- pickle pot and polishing: relatively safe; jeweller's torch and thermal shock: avoid; note: avoid heat, which may change the colour
- artificial light: relatively safe; heat in the display case and sunlight: use caution
any treatment state
- Warm soapy water is recommended; ultrasonic and steam cleaners are not
- Heat can alter the colour of some zircon; it is generally stable in light and to chemicals
- Mohs 6 to 7.5 with fair to good toughness; it can be brittle, so wear and store it where it will not rub hard against other materials
treated (Only after these treatments: heating)
- care (cleaning) §6.2 j
- Some heat-treated stones revert to their original colour (usually light brown) after long exposure to bright light
- may fade or revert to its original colour in strong light; do not wear or leave it in strong light for extended periods §6.2 f
- cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care §6.2 b
- All heat-treated stones need special care (SC): yellow stones, avoid harsh abrasives; blue and colourless stones, avoid strong UV light; red and pink stones, avoid both
- heated stones: some revert to their original colour in light
Durability and wearing
Toughness
Fair to good toughness; brittle
Treatments and identification leads
Registered treatmentsThe treatments registered for Zircon are heat treatment and irradiation. Stability and frequencyHeat treatment has the status treated, stability unstable and prevalence always; its identification leads include that the great majority of blue zircon is produced by heat treatment, that heating can also produce colourless, red, brown, yellow and other colours, and that the colour after treatment is usually stable, though in a few cases it changes on exposure to light. Values not givenIrradiation has the status irradiated or dyed, with stability and prevalence both shown as “—”, meaning the cited source gives no value, not “none”; its identification leads include that irradiation can turn colourless zircon deep red, brownish red, purple or orange-yellow, and can also turn blue zircon brown to reddish brown, and that the colour is unstable and hard to detect. The sources for both heat treatment and irradiation point to the corresponding treatment clauses of GB/T 16553—2017.
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| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| heatingStatus: treated | always | unstable | Optimization | heating (colourless, red, yellowish brown, blue, yellow, green) | See identification leads |
| irradiationStatus: irradiated or dyed | — | — | Treatment | — | See identification leads |
Where each treatment acts (schematics): Heated / Heat-treated · Irradiated
“—” means the cited source gives no value for that item, not “none”. Source: CIBJO Gemstone Book 2022 · GB/T 16553—2017; GB/T 16552—2017 Table B.1; JJA/AGL 2025
Whether a treatment has to show in the name differs between the two rule sets (this site’s paraphrase):
- GB/T 16552—2017: a method classed as treatment has to be stated in the name itself — the method put before the name, or added in brackets after it; a method classed as optimization does not need to appear in the name, though one marked “Optimization (annotation required)” still has to be noted in the quality documents. Source: §5.4.2.1 a), b); §5.4.2.2 a)
- CIBJO Gemstone Book 2022: no longer splits treatments into ones that need specific disclosure and ones that need only general disclosure: every treatment is to be disclosed, and the seller tells the buyer which treatment was used and what special care it calls for. Source: §4.2.5 Note 2, §4.2.5.1, pp.14–15
What this table covers
What this page can give
- Registered treatments, their stability and how often they occur (see the table above)
- Identification leads for each treatment, for use when sending a stone for testing
How lab reports word it
A general LMHC wording rule also covers Zircon (Information Sheet #8): see the LMHC rule “When colour authenticity cannot be determined”.
A general LMHC wording rule also covers Zircon (Information Sheet #16): see the LMHC rule “Colour stability testing”.
VerifyNames, standards, technical facts, clauses and sources
Names
Besides Zircon, the name register records "Blue Zircon" and "Starlite", for which no restriction on use as a name is recorded (CIBJO Gemstone Book 2022 Annex 8 “Blue Zircon”; CIBJO Gemstone Book 2022 Annex 8 “Starlite”).
Standard and listing namesThe GB/T 16552—2017 formal name for Zircon is zircon (Table A.1), CIBJO Gemmological Laboratories Book 2024 lists it item by item as Zircon, and the suggested listing name is simply Zircon. Names in four languagesFour-language names are given in Simplified Chinese, Traditional Chinese, English (Zircon) and Japanese; the formal name of Japan's GSJ is written as a separate Japanese form. National standard namesGermany (RAL) writes Zirkon and the EU writes Zircon. Institution usageOn authority wording, CIBJO records Zircon, the FTC text on file has no wording for this name, and GIA and Gem-A are unchecked; bodies without a recorded wording show the entry's own English name, which does not represent their position. Sub-names and unacceptable namesIn the name register, Blue Zircon is an English subordinate name (variety/subtype) and Starlite a market name; both are matched automatically with no registered restriction. Trade and mineralogical namesThe mineralogical name is Zircon (ZrSiO4).
Name register
Every name recorded for this entry, with how it is classified, whether it may be matched to this entry automatically, whether it may be used as a product name, and the clause it rests on.
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| Name | Type | Matching | Use as a name | Basis |
|---|---|---|---|---|
| no restriction recorded (2) | ||||
| Blue ZirconEnglish | narrower name (variety or subtype) | matched automatically | no restriction recorded | CIBJO Gemstone Book 2022 Annex 8 “Blue Zircon” |
| StarliteEnglish | market name | matched automatically | no restriction recorded | CIBJO Gemstone Book 2022 Annex 8 “Starlite” |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- ジルコン／風信子石
- Chinese formal name
- 锆石 (GB/T 16552—2017 Table A.1)
- Mineralogical name
- Zircon (ZrSiO4)
- Trade names and synonyms
- Blue Zircon (narrower name (variety or subtype)) · Starlite (market name)
Four-language names
- 简体中文
- 锆石
- 繁體中文
- 鋯石
- English
- Zircon
- 日本語
- ジルコン／ジルコン
National and regional formal names
- Germany (RAL)
- Zirkon
- European Union
- Zircon
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural inorganic gem materials
- Browsing family
- Other silicate minerals
- Identity tier
- Mineral species
- Mineral chemical class
- Silicates
- Construction or treatment status
- Natural; common industry optimization (verify with certificate)
Treatments listed by standards
GB/T Table B.1For Zircon, the "Zircon" row of GB/T 16552—2017 Annex B, Table B.1 lists heating and irradiation: heating improves or changes colour, category optimization; irradiation changes colour, category treatment. JJA/AGL designationsIn the "principal gem names" table of the Japanese JJA/AGL Definitions and Nomenclature of Gems and Ornamental Materials, November 2025 revision, the gem name is Zircon and the species zircon; colourless, red, yellowish brown, blue, yellow and green are registered as heating (heat treatment), and other colours are registered under the "no treatment" category. GB/T Table B.1What Table B.1 is, and how its grades are defined, are on the Gem treatments page, as is how to read the JJA/AGL table.
GB/T 16552-2017, Annex B, Table B.1
Table B.1, row “Zircon” (p.15):
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| Method | Effect | Category |
|---|---|---|
| Heating | Improves or changes colour | Optimization |
| Irradiation | Changes colour | Treatment |
What Table B.1 is, and how the “see 5.4.1” grades are defined: see the GB/T 16552: optimization vs treatment page.
JJA/AGL (Japan) table of principal gem names, 2025
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| Gem name | Species | Colour | Listed in the table | Notes |
|---|---|---|---|---|
| [colour] Zircon | Zircon | colourless, red, yellowish brown, blue, yellow, green | the source lists no untreated tier; heating (Heated / Heat-treated) | |
| [colour] Zircon | Zircon | other colours | an untreated tier is listed |
JJA/AGL definitions and nomenclature (2025 revision), table of principal gem names, p.13
How to read the JJA/AGL table: see the Gem treatments page.
What it is and how it's identified
The registered material facts for Zircon are: composition ZrSiO4, which may contain Ca, Mg, Mn, Fe, Al, P, Hf, U, Th and other elements; the structure is crystalline, though radioactive trace elements can lower its degree of crystallinity, by which it can be divided into high, medium and low types; the crystal system is tetragonal, with crystals mostly tetragonal dipyramidal, prismatic or tabular-prismatic. Zircon has a Mohs hardness of 6–7.5 and no cleavage; this site notes that hardness alone is not enough to judge durability. Zircon has a density of 3.9–4.73 g/cm³; this site notes that the cited clause gives a typical value under normal conditions, not an absolute limit, and that the clause has further sub-grades, with the overall value registered. The optic character of Zircon is anisotropic, uniaxial positive, birefringence is 0.001–0.059, and it is transparent. For untreated Zircon, pleochroism is generally weak and varies with body colour, the lustre is vitreous to adamantine, and magnification shows gas-liquid inclusions and mineral inclusions; high-type Zircon shows distinct doubling, medium and low types may show straight zoning and cloud-like inclusions, and the material is brittle, with facet edges prone to abrasion.
Registered material facts
Each row carries its own source and check date and can be cited on its own; “—” means the cited source gives no value, not “none”.
Definition
Zircon — nomenclature status: IMA status G: grandfathered (described before the IMA existed, and generally regarded as a valid species).
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Zircon — composition (chemistry): ZrSiO4, elements such as Ca,Mg,Mn,Fe,Al,P,Hf,U and Th may be contained.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — composition (phase): zircon
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Zircon — structure (overall): crystalline. Radioactive trace elements lower the degree of crystallization, and by that degree the gemstone can be classed as high, medium or low type.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-22
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-22)
- Fact checked on
- 2026-09-22
Zircon — structure (crystal system): tetragonal
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — structure (crystal habit): usually tetragonal bipyramids, prisms and flattened prisms.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Durability
Zircon — Mohs hardness: 6–7.5
GB/T 16553—2017
Reference points on this site: Talc 1–3, Fluorite 4, Apatite 5–5.5, Orthoclase 6–6.5, Topaz 8, Diamond 10 (Source: GB/T 16553—2017); Gypsum 1.5–2, Calcite 3, Quartz 7 (Source: Handbook of Mineralogy); Corundum 9 (Source: GIA Gem Encyclopedia (care guide))
- Does this standard apply
- applies to this entry
- General note
- hardness only, not durability
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — cleavage: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
For Zircon, the stability of heating is “unstable”.
CIBJO Gemstone Book 2022
- Treatment state
- treated
- Treatment
- heating
- Qualification
This says how well the treatment holds up, not how durable Zircon itself is.
- General note
- no durability verdict here
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Physical properties
Zircon — density: 3.9–4.73 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives this as a typical value. It is a common value, not an absolute limit.
- General note
- the clause has finer ranges
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Zircon — optic character: uniaxial, optically positive (anisotropic)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — birefringence: 0.001–0.059
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — transparency: transparent.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Zircon — pleochroism: generally weak, and varying with color: blue is strong, showing blue and brownish-yellow to colorless; green is very weak, showing green and yellow-green; orange to brown is weak to moderate, showing purple-brown and brown-yellow; red is moderate, showing purple-red and purplish-brown.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-22
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-22)
- Fact checked on
- 2026-09-22
Zircon — fluorescence (overall): blue: long wave none to moderate, light blue; short wave none; green: generally none; yellow, orange-yellow: none to moderate, yellow, orange; red, orange-red: none to strong, yellow, orange; brown: none to very weak, red.
GB/T 16553—2017
UV fluorescencelight bluenone–moderate, blueyelloworangenone–moderate, yellow, orange-yellowyelloworangenone–strong, red, orange-redrednone–very weak, brownDots are illustrative colours built from the colour names, not measured values
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — spectrum (UV-visible): visible from 2 to more than 40 absorption peaks; characteristic 653.5 nm absorption peak.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — spectrum (infrared): diagnostic bands of zircon in the mid-IR
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — optical effect (chatoyancy): seen; rare
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — magnification: gas-liquid inclusions, mineral inclusions; high-type zircon: obvious birefringence; medium- and low-type zircon: visible flat zonation, visible flocculent inclusion; brittle, with edges and corners that wear easily.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
body colour2 sources compared
Zircon — body colour: Colourless, blue, yellow, green, brown, orange, red.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Andesine, Topaz, Grossular and other entries also name colourless.
- General note
- colour alone is not identity
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Zircon — body colour: colorless, blue, yellow, green, brown, orange, red, purple, etc.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- Qualification
In chapter 5 of GB/T 16553—2017, the colour entries of Spinel, Garnet, Scapolite and other variety clauses also name colourless.
- General note
- colour alone is not identity
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
How the sources relate
- CIBJO Gemmological Laboratories Book 2024 and GB/T 16553—2017
Both list colourless, blue, yellow, green, brown, orange and red; GB/T 16553—2017 also lists purple.
- CIBJO definitions
- chatoyancy
Quality factors
Zircon — quality factor (lustre): vitreous to adamantine
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Testing and market
The tests the CIBJO laboratory protocol requires for Zircon, and what each method means, are in the protocol table on the laboratory testing page; the protocol requires a focused check for heating in Zircon, with a note on testing methods listing the special optical effect chatoyancy. On irradiation, colourless Zircon can turn deep red, brownish red, purple or orange-yellow, and blue Zircon brown to reddish brown; the colour is unstable and hard to detect. On heating, almost all blue Zircon is produced by heating, and colourless, red, brown, yellow and other colours can also be obtained by heating; the colour is stable in most cases, though a small number change after exposure to light. No synthetic Zircon is available on the market; for treated material, heating of Zircon in trade occurs always. The identification leads for heating and irradiation are cited from GB/T 16553—2017, which can be followed for Zircon as a reference only and does not govern it directly.
The tests the CIBJO laboratory protocol requires for this material, and what each method means, are in the protocol table on the laboratory testing page: §6.1.91.
How far testing can go
Zircon that has undergone irradiation can be identified by the following features: Irradiating colourless zircon can turn it deep red, brownish red, purple or orange-yellow, and irradiating blue zircon can turn it brown to reddish brown; the colour is not stable and the treatment is not easy to detect.
GB/T 16553—2017
- Treatment state
- irradiated or dyed
- Does this standard apply
- can be followed as a reference only
- Treatment
- irradiation
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (irradiation) (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon that has undergone heating can be identified by the following features: Nearly all blue zircon is produced by heating, which can also give colourless, red, brown and yellow; the result is usually stable, though a few stones change after exposure to light.
GB/T 16553—2017
- Treatment state
- treated
- Does this standard apply
- can be followed as a reference only
- Treatment
- heating
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.12 (heating) (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zircon — synthetic counterpart on the market: No synthetic counterpart of this material is commercially available
CIBJO Gemstone Book 2022
- Treatment state
- any treatment state
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
For Zircon in trade, the reported frequency of heating is “always”.
CIBJO Gemstone Book 2022
- Treatment state
- treated
- Treatment
- heating
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Zircon — what the CIBJO laboratory protocol says to watch for: heat treatment
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Zircon — notes on test methods in the CIBJO laboratory protocol:
| Test method | What the protocol notes for it |
|---|---|
| Phenomena: | Cat’s-eye |
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Clause-level definitions
Zircon has a direct definition in the CIBJO Gemmological Laboratories Book 2024 under the entry Zircon: colourless, blue, yellow, green, brown, orange, red, transparent, with chatoyancy possibly seen occasionally; the cross-check result is: defined directly by CIBJO, and also appears in the GB/T annex. Zircon is also registered under the IMA Mineral List entry as Zircon Zr(SiO4), cross-checked against the RRUFF and IMA master mineral list, using public domain data.
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Zircon | 7.2.1.266 | Colourless, blue, yellow, green, brown, orange, red, transparent; may rarely show chatoyancy | Defined directly by CIBJO; also present in the GB/T annex. |
| Zircon | IMA Mineral List entry | Zircon Zr(SiO4) G 1789 | Cross-checked against the RRUFF/IMA master mineral list (public domain data). |
Evidence and sources
Authority basis and clause sources
Sources
Further reading
Recorded cultural contexts
The U.S. Jewelers of America roster lists Blue Zircon for December; and Japan's JJA 2021 revised roster lists Zircon for December. This records trade-association convention only; it does not establish material identity, natural origin, treatment, provenance, or effect.
This table scrolls sideways on narrow screens.
| Publisher or holder | Region | From / period | Source and locator |
|---|---|---|---|
| Jewelers of America | United States | from 1952 | Jewelers of America, “Birthstone Jewelry” (web page, consulted 2026-08-22) Birthstone roster table, December row: Blue Zircon |
| Japan Jewellery Association | Japan | from 20 December 2021 | Tanjoseki (Japanese birthstone roster, Japan Jewellery Association page; revision of 20 December 2021) 2021 revised birthstone roster, December row: Zircon |
Related entries and topic cluster
Parent entry and related pages on this site. Rows marked “Planned” are suggested new content and have no link yet.
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Other silicate minerals | Live |
| Treatments recorded for this material | Heated / Heat-treated, Irradiated | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Zircon entry are maintained by the LumaLark wiki and matched one by one to the standard clauses or institutional sources they cite: every fact carries its source (with a clause or page locator) and a check date, so it can be traced back to the original; clause-level definitions also carry a cross-check result. The entry exists so that buyers and sellers can check naming, disclosure and material facts item by item.