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UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Mineral / gemstone variety · Natural identity; treatment status unknown
Black Opal
Also known asBlack crystal opal
A variety of natural opal with a dark body colour, basic name “black opal” in Table A.2 of GB/T 16552-2017; the dark colour may be natural or the result of treatment. 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 Black 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 Black OpalIdentification points from the research literature; how far lab testing can go
- Treatments and enhancements of Black Opal1 registered treatments: status, stability, how common they are and identification leads
- Caring for and wearing Black OpalCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of Black OpalEach value with its source and check date
- Black Opal 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?
- Listing and disclosing Black OpalThe listing name to use; what must be disclosed before sale
- Standard clauses that define Black 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
Black opal is a natural opal variety whose play-of-color shows over a bodycolor background that is black or another dark tone. Its play-of-color works as in precious opal generally: ordered stacks of sub-microscopic silica spheres (about 250 nm) diffract visible light into spectral colours, and the dark or black background makes that play-of-color stand out. As to origin, opal overall is hydrated amorphous silica laid down where rainwater-dissolved silica collects in cracks and between layers of underground rock, then consolidating as it loses water—it is not a crystalline mineral. Note: no source specific to black-opal localities (e.g. Lightning Ridge) has been found, so nothing beyond general natural-opal formation is claimed here about black opal's specific setting.
Scope: Applies to the body-colour definition of natural black opal and to general explanations of opal play-of-colour and genesis; does not apply to assertions about localities and ore-forming environments specific to black opal (no dedicated source on these has been found).
Sources GIA Opal Description · G&G Fall 2013
Where it forms
The formation setting common to natural opal (silica-bearing groundwater depositing in rock cracks and between layers), with the dark bodycolor being black opal’s varietal trait
Sources GIA Opal Description
How it forms, step by step
Natural opal forms as silica-bearing water deposits silica in rock cracks and between layers.
Sources GIA Opal Description
Silica spheres stack in order; a black/dark bodycolor acts as the background that makes the play-of-color stand out.
Sources GIA Opal Description
Light diffracting between the ordered spheres produces spectral colors that change with viewing angle.
Sources GIA Opal Description
Link to appearance
Black opal’s vivid play-of-color benefits from the dark bodycolor background setting off the diffracted colors; the play-of-color itself still comes from diffraction by ordered silica spheres.
Sources GIA Opal Description · G&G Summer 2025
Timescale
The cited sources give no absolute timescale for black opal or natural opal formation.
Sources GIA Opal Description · G&G Fall 2013
Supporting findings
Natural opal is hydrated amorphous silica, deposited from silica dissolved by rainwater into cracks and between layers of underground rock and consolidated as it loses water; it is not a crystalline mineral.
Evidence grade AScope: General natural-opal formation; not used to infer black opal’s specific setting.
Sources GIA Opal Description · G&G Fall 2013
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Africa
- Shewa, Ethiopia
Sources GIA Gem Encyclopedia
- Stayish mine, Wollo, Ethiopiaproducing black opal since 2013
Sources G&G Winter 2023
Oceania
- Lightning Ridge, New South Wales, AustraliaGIA: famed for prized black opal (not stated as main source)
Sources GIA Gem Encyclopedia
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
Opal’s play-of-color comes from diffraction of visible light by ordered stacks of sub-microscopic silica spheres; monodisperse spheres of about 250 nm (or opal-CT lepispheres) form 3D photonic crystals.
Evidence grade AScope: The mechanism is general to natural opal, not black-opal-specific; the dark-background enhancement is described qualitatively.
How it is identified
Black opal can resemble treated or imitation dark material, so appearance is not a sound basis for identification. A laboratory tests composition and structure and uses microscopy with instrumental analysis to separate natural black opal, treated material and imitations; the verdict must come from an accredited body.
Evidence grade AScope: Whether black opal is treated or imitation must be judged by an accredited laboratory; no self-identification basis is provided.
Other research findings
A natural opal variety, black opal is translucent to opaque, its play-of-color appearing over a background that is black or another dark hue.
Evidence grade AScope: A GIA descriptive definition; it gives no locality or formation detail.
Sources GIA Opal Description
Lightning Ridge, Australia, is a well-known black opal source; a rare black opal suite from there took years to collect, reflecting low production.
Evidence grade CScope: Only a trade/market mention of Lightning Ridge black opal; the black-opal-specific geological source is missing, hence grade C.
Since 2013 the Stayish mine, located in Ethiopia's Wollo province, has yielded black opal—an additional locality for the material.
Evidence grade CScope: The source is a related-item note in a GIA article, not a black-opal-specific study, hence grade C.
Sources G&G Winter 2023
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- Sources specific to black-opal localities and formation (Lightning Ridge, etc.) are not available, so no black-opal-specific formation setting is asserted; all related locality statements are graded C.
- The play-of-color and formation statements for black opal here are drawn from general natural-opal sources, and no other variety’s specific facts are passed off as black opal facts.
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
- Black Opal
GB/T 16552—2017 Table A.2 “Black Opal” · IMA Mineral List 2026-07 “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), Heated / Heat-treated, Impregnated
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
Black Opal is Dark-background natural opal variety; use "Black Opal" for listings, and disclose any known treatments.
Evidence
- GB/T · Table A.2, row 黑欧泊 (Black Opal)
What this means for you
Before buying, check the recommended listing name "Black 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 Black Opal, is set out in full under care on the Opal entry.
Care
Black 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, Black Opal, p.62; §6.2 k (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
Black Opal — care (special care): impregnated with colourless plastic to improve durability and appearance: special care (SC); avoid heat.
AGTA Gemstone Information Manual, 17th ed.
- Treatment state
- treated
- Only after these treatments
- impregnation
Source & check 2026-09-26
- Source
- AGTA Gemstone Information Manual, 17th edition (August 2026) (AGTA): p.XII, Gemstone Information Chart, Opal White, Black & Semi-Black I, CARE REQUIRED / SPECIAL ADVICE (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Black Opal — care (special care): impregnated with colourless oil, wax or resin: special care (SC); avoid heat.
AGTA Gemstone Information Manual, 17th ed.
- Treatment state
- treated
- Only after these treatments
- fissure filling with oil, fissure filling with resin
Source & check 2026-09-26
- Source
- AGTA Gemstone Information Manual, 17th edition (August 2026) (AGTA): p.XII, Gemstone Information Chart, Opal White, Black & Semi-Black O, CARE REQUIRED / SPECIAL ADVICE (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
Care conclusions for Black Opal are given by treatment state. CIBJOThe CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) states that for treated Black Opal (impregnation only), treatments such as dyeing, oiling, resin, wax or plastic impregnation are not permanent, so keep it away from all solvents (including detergents of every kind), chemicals and heat. AGTAThe American Gem Trade Association Gemstone Information Manual, 17th edition, states that treated Black Opal impregnated with colourless plastic to improve durability and appearance (impregnation only) needs special care (marked SC) and should be kept away from heat; it also states that treated Black Opal impregnated with colourless oil, wax or resin (oil or resin fracture filling only) needs special care (marked SC) and should be kept away from heat. CleaningThe Gemological Institute of America care and cleaning guide is given for opal as a whole class and applies equally to Black Opal; see the care section of the Opal entry for the details.
This table scrolls sideways on narrow screens.
| 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 |
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.
treated (Only after these treatments: impregnation)
- Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat §6.2 k
- impregnated with colourless plastic to improve durability and appearance: special care (SC); avoid heat
treated (Only after these treatments: fissure filling with oil, fissure filling with resin)
Treatments and identification leads
Registered treatmentsThe treatment registered for Black Opal is impregnation: its status is treated, its stability is unstable and its market prevalence is rare. Values not givenThe identification leads and source for impregnation are entered as “—”, meaning the cited source gives no value, not “none”.
This table scrolls sideways on narrow screens.
| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| impregnationStatus: treated | rarely | unstable | — | impregnation with a colourless agent; impregnation with a coloured agent | — |
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Dyeing | — | — | Treatment | — | — |
| Coating | — | — | Treatment | — | — |
| heating | — | — | — | heating | — |
| soaking in sugar solution | — | — | — | soaking in sugar solution | — |
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); 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
VerifyNames, standards, technical facts, clauses and sources
Names
Besides Black Opal, the name register records "Black crystal opal", for which no restriction on use as a name is recorded (CIBJO Gemmological Laboratories Book 2024 §7.2.1.30 “Black crystal opal”).
Standard and listing namesThe GB/T 16552—2017 formal name for Black Opal is the Table A.2 name for black opal, and the suggested listing name is Black Opal; the mineralogical name refers to a natural opal variety with a dark background. Names in four languagesThe four-language names are given in Simplified Chinese, Traditional Chinese, English (Black Opal) and Japanese (a transliteration), the Japanese being the GSJ (Japan) formal name. Australia (GAA) writes Black Opal, and the Lightning Ridge name is protected under NSW law. Sub-names and unacceptable namesThe register also has the English subordinate name (variety or subtype) Black crystal opal, which can be matched automatically, based on the CIBJO Gemmological Laboratories Book 2024, with no restriction on its use as a name recorded. Institution usageAmong authority wordings, GIA and CIBJO list Black Opal, with CIBJO adding that treatment must be disclosed; the FTC source text has been checked and does not use the wording Black Opal; Gem-A's wording has not yet been checked. Bodies without a recorded wording show Black Opal's own English name, which does not represent their position.
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.
This table scrolls sideways on narrow screens.
| Name | Type | Matching | Use as a name | Basis |
|---|---|---|---|---|
| no restriction recorded (1) | ||||
| Black crystal opalEnglish | narrower name (variety or subtype) | matched automatically | no restriction recorded | CIBJO Gemmological Laboratories Book 2024 §7.2.1.30 “Black crystal opal” |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- ブラックオパール
- Chinese formal name
- 黑欧泊 (GB/T 16552—2017 Table A.2)
- Mineralogical name
- Dark-background natural opal variety
- Trade names and synonyms
- Black crystal opal (narrower name (variety or subtype))
Four-language names
- 简体中文
- 黑欧泊
- 繁體中文
- 黑歐泊
- English
- Black Opal
- 日本語
- ブラックオパール
National and regional formal names
- Australia (GAA)
- Black Opal; Lightning Ridge designation protected under NSW law
Qualifiers stripped from the headline name
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
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.
JJA/AGL (Japan) table of principal gem names, 2025
This table scrolls sideways on narrow screens.
| Gem name | Species | Colour | Listed in the table | Notes |
|---|---|---|---|---|
| Black Opal | Opal | dark to black | an untreated tier is listed; heating (Heated / Heat-treated); soaking in sugar solution (no matching treatment page on this site); impregnation with a colourless agent (Impregnated); impregnation with a coloured agent (Impregnated) | play of colour |
JJA/AGL definitions and nomenclature (2025 revision), table of principal gem names, p.9
How to read the JJA/AGL table: see the Gem treatments page.
What it is and how it's identified
Registered material facts for Black Opal: composition opal; structure amorphous, for opal (the whole class). Body colour black, dark grey, blue, green, brown or other dark colours, untreated; transparency translucent to opaque. Mohs hardness 5–6.5, from a clause covering the whole species, of which Black Opal is only one variety; no cleavage, for opal (the whole class). Density 1.25–2.23 g/cm³, for opal (the whole class): clause value 2.15, tolerance +0.08, −0.90, range worked out from that. Refractive index 1.37–1.47, for opal (the whole class): clause value 1.450, tolerance +0.020, −0.080, range worked out from that; site note: the clause also gives finer sub-ranges, and the overall value is used. No birefringence, optic character isotropic, with anomalous extinction often seen in fire opal, all for opal (the whole class); no pleochroism, untreated, for opal (the whole class). The optical effect (play-of-colour) is visible, for opal (the whole class); lustre vitreous to resinous, untreated, for opal (the whole class).
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 Black 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 Black Opal (how to read class-level values).
Definition
Black Opal: opal with a black, dark grey, blue, green, brown or other dark body colour.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 Colour · Black opal (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
Black Opal — composition (phase): opal
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Black 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
Black 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
Black 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
Black 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 Black 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
Black 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
Black 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
Black 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
Black 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
Black Opal — transparency: translucent to opaque.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Black 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
Black Opal — fluorescence (overall): black or white body colour: none to moderate, white to light blue; green, yellow; may be phosphorescent; black opal of other body colour: none to strong, green, yellow-green; may be phosphorescent.
GB/T 16553—2017
UV fluorescencewhitelight bluenone–moderate, black or white body colourgreenyellowblack or white body colourgreenyellow-greennone–strong, black opal of other body colourDots are illustrative colours built from the colour names, not measured values
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.3 Fluorescence (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
optical effect (play of colour)2 sources compared
Black 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
Black 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
Black 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
Black Opal — body colour: a dark body colour: black, dark grey, blue, green, brown or similar.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Carbonado, Nuummite, Andradite and other entries also name black or a blackish colour.
- 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
Black 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
In the CIBJO laboratory protocol, laboratory identification of Black Opal falls under “Opal”: for identification see the Opal entry, and the required tests are listed on the laboratory testing page. Among Black Opal on the market, impregnation (treated) occurs with a prevalence of “rare”.
The CIBJO laboratory protocol covers Black 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 Black 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
Black Opal has a clause-level definition in the CIBJO Gemmological Laboratories Book 2024 under the term Black opal, summarised as mineral species opal, mineral/gem variety black opal, with the CIBJO wording quoted in full under Clause-level definitions on this page; the cross-check result is a direct CIBJO definition, also present in the GB/T annex. The CIBJO Gemmological Laboratories Book 2024 also lists Black crystal opal, summarised as strong play-of-colour against a dark body colour; the cross-check result is a direct CIBJO definition, with no identically named English entry found in the GB/T annex.
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Black opal | 7.2.1.29 | Play-of-colour against a black, dark grey, blue, green, brown or other dark body colour, translucent to opaque | Defined directly by CIBJO; also present in the GB/T annex. |
| Black crystal opal | 7.2.1.30 | Strong play-of-colour against a dark body colour | 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 (Black Opal) is marked.
This table scrolls sideways on narrow screens.
| 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), Heated / Heat-treated, Impregnated | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Black 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.