On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Mineral / gemstone variety · Natural identity; treatment status unknown
Crystal Opal
Also known asWater opal
A transparent to translucent opal variety with strong play-of-color; the transparency grade and the authenticity of the play-of-color must be confirmed piece by piece. 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 Crystal Opal 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 Crystal OpalIdentification points from the research literature; how far lab testing can go
- Treatments and enhancements of Crystal Opal1 registered treatments: status, stability, how common they are and identification leads
- Caring for and wearing Crystal OpalCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of Crystal OpalEach value with its source and check date
- Crystal Opal in English, Chinese and Japanese; national standard namesNames in four languages, the GB/T standard name and the suggested listing name; and: Which of GIA, FTC, CIBJO and Gem-A have a name for it on record, and do those agree?
- Listing and disclosing Crystal OpalThe listing name to use; what must be disclosed before sale
- Standard clauses that define Crystal OpalWhich 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
Crystal opal (also called water opal) is a variety of opal characterized by a transparent to semitransparent, clear background together with exceptional play-of-color. It forms the same way as other opal: a silica-bearing fluid (silica gel) fills cavities and layers in rock, water evaporates, and silica is deposited as tiny spheres; when these spheres are stacked in a regular grid-like pattern, visible light diffracts between them and produces play-of-color. The clear, highly transparent background reflects more uniform silica packing with fewer inclusions and pores that lets light pass through. The color seen varies with sphere size—about 0.1 micron produces violet and about 0.2 microns produces red. The name is a variety/appearance class of opal, not an independent mineral kind.
Scope: Used to explain the natural opal variety that is transparent to translucent, with a clear background and play-of-colour; this name is a variety/appearance classification of opal, and the material it refers to is still mineralogically opal (hydrated amorphous silica).
Sources GIA Opal Description · GIA Opal
Where it forms
Australian-style sedimentary setting: seasonal rains soak into ancient underground sedimentary rock and silica precipitates in cracks and between layers.
Sources GIA Opal Description
Volcanic or volcaniclastic host-rock settings (e.g. Ethiopia): silica gel deposits as opal within cavities in the rock.
Sources GIA Opal
How it forms, step by step
A silica-bearing fluid fills cracks, layers or cavities in the rock.
Sources GIA Opal
Evaporation of the water leaves silica behind as minute spheres.
Sources GIA Opal
The spheres stack in a regular grid-like pattern; visible light diffracts between them, producing play-of-color.
Sources GIA Opal Description
Where silica packing is more uniform and there are fewer inclusions and pores, the material is transparent to semitransparent with a clear background, and is classed as crystal opal.
Sources GIA Opal Description
Link to appearance
A transparent to semitransparent, clear background with exceptional play-of-color flashes; the color varies with silica sphere diameter (about 0.1 micron gives violet, about 0.2 microns gives red).
Sources GIA Opal Description
Timescale
The cited sources describe opal formation through alternating seasonal rains and dry periods and precipitation between rock layers, but give no numeric age or absolute timescale for crystal opal formation.
Sources GIA Opal Description
Related base materials
- Opal (hydrated amorphous silica, SiO2·nH2O): variety-of | Crystal opal is the variety of opal characterised by a transparent to semi-transparent, clear background; the material itself is still opal
Supporting findings
Opal (including crystal opal) forms when silica dissolved by seasonal rains precipitates in cracks and between layers of underground rock.
Evidence grade AScope: Describes opal formation in the Australian sedimentary setting; other genetic types are not covered by this source.
Sources GIA Opal Description
During opal formation, silica gel occupies crevices within rock, and once the water evaporates, silica is left deposited as minute spheres.
Evidence grade BScope: This is the GIA encyclopedia's overview description of opal formation, not locality-specific.
Sources GIA Opal
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Africa
- Wegel Tena, Wollo, Ethiopia
Sources Gems & Gemology Summer 2010
- Shewa, Ethiopia
Sources GIA Gem Encyclopedia
North America
- Virgin Valley, Nevada, United States
Sources Mindat: Opal
- Opal Butte, Oregon, United States
Sources Mindat: Opal
Oceania
- Lightning Ridge, New South Wales, Australia
Sources Mindat: Opal
- Coober Pedy, South Australia, Australia
Sources Mindat: Opal
- Mintabie, South Australia, Australia
Sources Mindat: Opal
- Yowah, Queensland, Australia
Sources Mindat: Opal
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
The play-of-color of precious opal comes from the diffraction of visible light by sub-microscopic silica spheres stacked in a grid, the color seen varying with sphere size.
Evidence grade AScope: Applies to regularly packed silica spheres; irregularly packed material shows no play-of-color.
Sources GIA Opal Description
How it is identified
Crystal opal is transparent with fine play-of-colour, and that look can equally be mimicked by laboratory-made or imitation products. Transparency and play-of-colour are not enough for a conclusion; separating natural, laboratory-made and imitation/composite material requires laboratory measurement of gemological properties and composition. The conclusion should be issued by a qualified gem laboratory; appearance cannot replace identification.
Evidence grade AScope: Applies where natural, synthetic and imitation opal must be distinguished; no self-administered criteria are given.
Other research findings
'Crystal or water opal' is defined as opal that is transparent to semitransparent with a clear background showing exceptional play-of-color—a variety of opal, not an independent mineral.
Evidence grade AScope: Defines a variety/appearance class name; the material it denotes is still mineralogically opal.
Sources GIA Opal Description
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- 'Crystal opal' is a variety/appearance class name of opal, not an independent mineral; the material it denotes is opal.
- The cited sources give no numeric age or absolute timescale for crystal opal formation.
- The link between a clear, transparent background and more uniform packing with fewer inclusions is a reasonable synthesis of known opal structure, not a sentence-level statement in the cited sources.
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
- Crystal Opal
IMA Mineral List 2026-07 “Opal” · CIBJO Gemmological Laboratories Book 2024 §7.2.1.68 “Crystal opal”
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Filled / Fracture-filled (via parent material), Dyed (via parent material), Coated (via parent material)
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
Crystal Opal is Transparent to semi-transparent opal with strong play-of-colour; use "Crystal Opal" for listings, and disclose any known treatments.
Evidence
- CIBJO · 7.2.1.68
What this means for you
Before buying, check the recommended listing name "Crystal Opal" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.
Known uncertainty
- 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.
The item-by-item care advice that the GIA Care and Cleaning Guide gives for the whole class, and so for Crystal Opal, is set out in full under care on the Opal entry.
Care
Crystal Opal — care (chemicals): Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code k
- Treatment state
- treated
- Only after these treatments
- impregnation
Source & check 2026-09-25
- Source
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Crystal opal, p.63; §6.2 k (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
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
ChemicalsFor the care of Crystal Opal, the CIBJO Official Gemstone Book (Coloured Stone Commission 2022) records, on contact with acids, alkalis and household chemicals, that for impregnated material, treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents, including dish-washing liquids, and from chemicals and heat. The treatment state is treated, limited to impregnated material. General careGeneral care that applies to all gems is in the general care paragraph on the materials index page; the GIA Care and Cleaning Guide gives its advice for the whole class, so it also applies to Crystal Opal, and the item-by-item advice is listed in full in the care part of the Opal entry.
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| Question | Matching entries |
|---|---|
| Contact with acids, alkalis and household chemicals | Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat |
Treatments and identification leads
Registered treatmentsThe registered treatment for Crystal Opal is impregnation. Stability and frequencyImpregnation has the status treated, its stability is marked “unstable” and its prevalence on the market “rare”. Values not givenThe registered values for identification leads and source are both “—”, meaning the cited source gives no value, not “none”.
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| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| impregnationStatus: treated | rarely | unstable | — | — | — |
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Dyeing | — | — | Treatment | — | — |
| Coating | — | — | Treatment | — | — |
Where each treatment acts (schematics): Impregnated
“—” means the cited source gives no value for that item, not “none”. Source: CIBJO Gemstone Book 2022; GB/T 16552—2017 Table B.1 (row for Opal)
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
VerifyNames, standards, technical facts, clauses and sources
Names
Besides Crystal Opal, the name register records "Water opal", for which no restriction on use as a name is recorded; one further name in a non-Latin script is listed in the name register below (1 with no restriction recorded on use as a name).
Names in four languagesCrystal Opal has Simplified Chinese, Traditional Chinese and Japanese names, and its English name is Crystal Opal. Standard and listing namesThe suggested listing name is Crystal Opal. Its GB/T naming counterpart is Opal (GB/T 16552—2017 Table A.2); the standard does not list Crystal Opal itself. Trade and mineralogical namesThe trade name or synonym is Water opal, an English market name, based on an editorial ruling by this site (no clause cited). Candidate search termsA Japanese transliteration of water opal, per the JJA/AGL Gemstone Nomenclature 2025, is a search candidate only. Trade and mineralogical namesThe mineralogical name describes transparent to translucent opal with strong play-of-colour. Institution usageFor authority wording, CIBJO records Crystal Opal (CIBJO Gemmological Laboratories Book 2024); the FTC text on file has no wording for Crystal Opal (checked); GIA and Gem-A are unchecked, and bodies without a recorded wording show the English name of Crystal Opal, which does not represent their position. Japanese namesThe GSJ (Japan) formal-name wording is not yet verified by this site; the Japanese name of Crystal Opal is a katakana transliteration.
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) | ||||
| Water opalEnglish | market name | matched automatically | no restriction recorded | editorial ruling (no clause cited) |
| ウォーター・オパールJapanese | transliteration | search candidate only | no restriction recorded | JJA/AGL Gemstone Nomenclature 2025 p.9 |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- クリスタルオパール (not yet checked for this body — the entry's own Japanese name is shown)
- GB/T naming counterpart (this name is not in the standard)
- 欧泊 (GB/T 16552—2017 Table A.2)
- Mineralogical name
- Transparent to semi-transparent opal with strong play-of-colour
- Trade names and synonyms
- Water opal (market name)
Four-language names
- 简体中文
- 水晶欧泊
- 繁體中文
- 水晶歐泊
- English
- Crystal Opal
- 日本語
- クリスタルオパール
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural inorganic gem materials
- Browsing family
- Opal and natural amorphous silica materials
- Identity tier
- Mineral / gemstone variety
- Mineral chemical class
- Not applicable
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
For Crystal Opal, this site applies the Opal row of GB/T 16552—2017, Annex B, Table B.1: filling, graded; dyeing, classed as treatment; coating, classed as treatment. The full effect description for filling is on the Opal page; what Table B.1 is and how the grades are defined are explained on this site's Gem treatments page.
GB/T 16552-2017, Annex B, Table B.1
Under the “Opal” row of Table B.1: Filling Graded — see §5.4.1, Table 1; Dyeing Treatment; Coating Treatment. The full row, with the effect column, is on the Opal page.
What Table B.1 is, and how the “see 5.4.1” grades are defined: see the GB/T 16552: optimization vs treatment page.
What it is and how it's identified
The material facts registered for Crystal Opal itself are: composition (phase) opal, transparency transparent to translucent, and optical effect play-of-colour. Registered under the clauses for opal (the whole category) are: structure (overall) amorphous; no cleavage; density 1.25–2.23 g/cm³ (clause value 2.15, allowed deviation +0.08/−0.90, from which the range is derived); refractive index 1.37–1.47 (clause value 1.450, allowed deviation +0.020/−0.080, from which the range is derived); no birefringence; optically isotropic; and, when untreated, the quality factor (lustre) vitreous to resinous. Mohs hardness is 5–6.5; this site notes that the cited clause covers the whole species, and crystal opal is only one variety within it.
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”.
Chemical composition, luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for opal (whole class), so they are not repeated on the Crystal Opal page; see the material facts on the Opal entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Crystal Opal (how to read class-level values).
Definition
Crystal Opal — composition (phase): opal
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Crystal Opal — structure (overall): amorphous (not crystalline)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Crystal Opal — Mohs hardness: 5–6.5
GIA Opal
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))
- Qualification
The clause we cite covers the whole species. This entry is only one variety of it.
Source & check 2026-09-20
- Source
- GIA Gem Encyclopedia — Opal (Gemological Institute of America): Section “FACTS”, “Mohs Hardness” (locator checked 2026-09-28)
- Fact checked on
- 2026-09-20
Crystal Opal — cleavage: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Crystal Opal — stability: chips and cracks easily; porous, so keep it away from coloured liquids; will craze if it loses water, so keep it away from heat and dry air; avoid sudden temperature changes; no ultrasonic cleaning.
CIBJO Gemstone Book 2022
CIBJO Gemstone Book §6.2:special-care code b, special-care code c, special-care code d, special-care code e, special-care code j
- Treatment state
- untreated
Source & check 2026-09-21
- Source
- Fact checked on
- 2026-09-21
For Crystal Opal, the stability of impregnation is “unstable”.
CIBJO Gemstone Book 2022
- Treatment state
- treated
- Treatment
- impregnation
Source & check 2026-09-25
- Source
- Fact checked on
- 2026-09-25
Physical properties
Crystal Opal — density: 1.25–2.23 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
- Qualification
The clause we cite gives 2.15, with a stated tolerance of +0.08 / -0.90. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Crystal Opal — optic character: isotropic; fire opal commonly shows anomalous extinction.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Crystal Opal — refractive index: 1.37–1.47
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
- Qualification
The clause we cite gives 1.450, with a stated tolerance of +0.020 / -0.080. The range shown here is worked out from that.
- General note
- the clause has finer ranges
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Crystal Opal — birefringence: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Crystal Opal — transparency: transparent to translucent.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Crystal Opal — pleochroism: none
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
optical effect (play of colour)2 sources compared
Crystal Opal — optical effect (play of colour): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Crystal Opal — optical effect (play of colour): play-of-colour.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Crystal Opal — optical effect (chatoyancy): seen; rare
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Crystal Opal — body colour: Strong play-of-colour against a colourless body.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Achroite, Goshenite, Rock Crystal and other entries also name colourless.
- General note
- colour alone is not identity
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
- CIBJO definitions
- play of colour, chatoyancy
Quality factors
Crystal Opal — quality factor (lustre): vitreous to resinous
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- opal (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 (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.
This material (RI / SG midpoints): 1.42 / 1.74; Closest values: 1Synthetic Opal 1.45 / 2.08, 2Mammoth Ivory 1.53 / 1.75, 3Ivory 1.535 / 1.85, 4Hackmanite 1.483 / 2.27, 5Chrysocolla 1.516 / 2.2
Show the full chart (330 registered materials)
Outside the full chart's range, drawn as triangles at the edge (RI / SG midpoints): Hematite 3.045/5.12, Synthetic Rutile 2.76/4.26, Rutile 2.753/4.23, Synthetic Moissanite 2.67/3.22
Testing and market
The CIBJO laboratory protocol covers Crystal Opal under “Opal” (§6.1.56): see identification on the Opal entry; the required tests are listed on the CIBJO laboratory protocol table for Opal.
How far testing can go
For Crystal Opal in trade, the reported frequency of impregnation is “rarely”.
CIBJO Gemstone Book 2022
- Treatment state
- treated
- Treatment
- impregnation
Source & check 2026-09-25
- Source
- Fact checked on
- 2026-09-25
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Clause-level definitions
Crystal Opal is listed in CIBJO Gemmological Laboratories Book 2024 under the entry name Crystal opal; the definition given is mineral species opal, trade name crystal opal (also called water opal), with the CIBJO wording quoted in full under Clause-level definitions on this page. The cross-check result is that it is defined directly by CIBJO; no identically named English entry was found in the GB/T annex.
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| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Crystal opal | 7.2.1.68 | Strong play-of-colour against a colourless body, transparent to translucent | Defined directly by CIBJO; no identically named English entry was found in this edition of the GB/T annex. |
Evidence and sources
Authority basis and clause sources
Sources
- CIBJO – The World Jewellery Confederation. Gemmological Laboratories Book (Blue Book), Gemmological Commission 2024-1.
- CIBJO – The World Jewellery Confederation. The Gemstone Book (Blue Book), 2022.
- SAMR / SAC (China). GB/T 16552—2017 Gems — Nomenclature.
- RRUFF Project, in partnership with the IMA – International Mineralogical Association. IMA Mineral List.
- Geological Survey of Japan, AIST (Japan). Museum mineral specimens, browse by classification.
Further reading
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.
Related-entry tree for Opal on this site: 17 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Crystal Opal) is marked.
- Opal
Sub-entries (16)
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| Page | Content | Status |
|---|---|---|
| Browsing family | Opal and natural amorphous silica materials | Live |
| Treatments recorded for this material | Filled / Fracture-filled (via parent material), Dyed (via parent material), Coated (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Crystal Opal 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.