On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Natural amorphous gem material / mineraloid · Natural identity; treatment status unknown
Coober Pedy Opal
A trade name for White Opal or Crystal Opal historically linked to Coober Pedy in South Australia; the name itself does not prove origin. 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 Coober Pedy 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 Coober Pedy OpalIdentification points from the research literature; how far lab testing can go
- Treatments and enhancements of Coober Pedy OpalThe enhancements and treatments the GB/T and JJA/AGL tables list
- Caring for and wearing Coober Pedy OpalCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of Coober Pedy OpalEach value with its source and check date
- Coober Pedy 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: Has any of GIA, FTC, CIBJO or Gem-A put a name for it on record here?
- Listing and disclosing Coober Pedy OpalThe listing name to use; what must be disclosed before sale
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
Coober Pedy opal is a commercial/trade name rather than a species: it denotes white or crystal opal that has historically been linked to Coober Pedy in South Australia, and the material itself is a variety of opal. This record's sources provide no formation account specific to the Coober Pedy locality. In general terms, opal is a water-bearing amorphous silica whose origin is complicated; geologically, specialists divide it into a 'sedimentary type' - the kind seen in many Australian fields of the Great Artesian Basin - and a 'volcanic type', such as that near Tintenbar in New South Wales and in parts of Mexico, the United States, Honduras, Ethiopia and Indonesia.
Scope: Applies to defining the identity of Coober Pedy opal as a commercial name, and gives the general composition of opal and the framework of sedimentary / volcanic environments; it does not constitute a conclusion on origin specific to the Coober Pedy locality (the cited sources have no specific content).
Sources G&G Fall 2019 · G&G Winter 2023
Where it forms
Sedimentary-type opal setting: experts classify numerous Australian opal deposits within the Great Artesian Basin as 'sedimentary-type'; Coober Pedy is a South Australian opal field, but this source set does not name it specifically.
Sources G&G Winter 2023
Setting of volcanic-type opal: for example near Tintenbar (New South Wales) and in parts of Mexico, the United States, Honduras, Ethiopia and Indonesia.
Sources G&G Winter 2023
How it forms, step by step
(Generic opal) Silica precipitates as amorphous, water-bearing hydrated silica from low-temperature aqueous fluids.
Sources G&G Winter 2023
(Sedimentary-type) Opal fills pores or fissures in sedimentary host rock or replaces pre-existing material.
Sources G&G Winter 2023
(Volcanic-type) Opal precipitates and concentrates in volcanic rocks and related structures.
Sources G&G Winter 2023
Coober Pedy opal enters the market as a white/crystal opal trade type; the source set provides no further formation detail.
Sources G&G Winter 2023
Link to appearance
Coober Pedy opal is mainly white or crystal (transparent) in body color; the prized look of opal comes from body color and play-of-color, which arises from diffraction by regularly arranged silica microspheres. The source set gives no Coober Pedy-specific appearance-formation link.
Sources G&G Fall 2019
Timescale
The cited sources give no formation age or duration for Coober Pedy opal or Australian sedimentary-type opal.
Sources G&G Fall 2019 · G&G Winter 2023
Related base materials
- Opal (hydrated amorphous silica): variety-of | Coober Pedy opal is a commercial name for white opal/crystal opal from the Coober Pedy area, attached to the mineral species opal
Supporting findings
On the basis of their geological setting, specialists separate opal of the 'sedimentary type' - the kind found in many Australian fields of the Great Artesian Basin - from opal of the 'volcanic type', such as that near Tintenbar in New South Wales and in parts of Indonesia, Mexico, the United States, Honduras and Ethiopia.
Evidence grade AScope: A general classification of opal geological settings; the Great Artesian Basin is the sedimentary background for South Australian opal including Coober Pedy, though the source does not name Coober Pedy.
Sources G&G Winter 2023
How precious opal comes to form is a complicated question that the report does not attempt to answer; in both volcanic and sedimentary hosts, features acting as lithological and structural 'traps' are considered essential to where opal mineralisation forms and how it is distributed.
Evidence grade CScope: The mechanism is drawn from a Slovak volcanic-hosted deposit and cannot be directly applied to Coober Pedy's sedimentary deposit; offered only as a general framework.
Sources G&G Winter 2023
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Oceania
- Coober Pedy, South Australia, AustraliaGIA cites the Coober Pedy fields for light opal; not called the main source
Sources GIA Opal Description
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
Coober Pedy opal is a trade name for white or crystal opal historically linked to Coober Pedy, South Australia; its main mineral is opal, so its play-of-color comes from diffraction of white light by opal's regularly arranged silica-sphere array, with sphere size and spacing setting the color range and shifting it with viewing angle. The locality name does not change this mechanism, and a light bodycolor merely means a different background, not a different physics.
Evidence grade AScope: Applies to material sold under this locality name that is mineralogically opal; the mechanistic account does not prove any specimen's locality, naturalness, or treatment.
Sources GIA Opal Description · G&G Summer 2025
Compared with black opal: the diffraction mechanism is the same, the difference being the bodycolor background—a dark background strengthens the contrast of the play-of-color, a light one makes it softer; Coober Pedy is known for white/crystal opal, so its play-of-color is usually seen against a light background. No Coober Pedy-specific optical data have been found, so this comparison is only a general rule.
Evidence grade BScope: A general statement about background contrast, not a locality-specific conclusion.
Sources GIA Opal Description
How it is identified
Coober Pedy (Australia) opal usually has a lighter background, and its appearance can resemble imitation or synthetic opal, so unaided inspection struggles to confirm a natural origin. Separation relies on laboratory testing such as measuring gemological properties and compositional analysis; natural-status and origin judgements depend on reference material with uncertainty, and conclusions must be issued by an accredited laboratory. This entry provides no self-identification method or threshold.
Evidence grade AScope: Appearance is insufficient to settle natural status and origin; determination requires testing by an accredited laboratory, and this entry gives no self-test method or threshold.
Other research findings
Coober Pedy opal is a commercial/trade name for white or crystal opal historically associated with Coober Pedy, South Australia, a variety term for opal rather than an independent mineral species.
Evidence grade CScope: A naming-boundary statement; the source set does not specifically discuss Coober Pedy, so this is grade-C inference and the trade-name status needs independent locality evidence.
Sources G&G Winter 2023
Opal is a form of amorphous silica that contains water, and when the water content is high the stone is prone to crazing and cracking if allowed to dry out.
Evidence grade AScope: A general property of opal material, applicable to all natural opal including material from Coober Pedy; not locality-specific.
Sources G&G Fall 2019
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- No dedicated Coober Pedy source has been found, and the cited sources have no Coober Pedy-specific content, so virtually all locality/formation statements are grade C.
- Formation age, duration, and the specific geological setting of Coober Pedy opal lack source support.
- 'Coober Pedy opal' is a trade name; its locality attribution must be independently confirmed.
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
- Opal (any geographic-origin claim requires a laboratory opinion)
16 CFR Part 23 §23.1
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
"Coober Pedy Opal" is a market name rather than a mineral species name; before using it, verify: Laboratory identification required before the name is used.
Evidence
What this means for you
Before buying, check the recommended listing name "Opal (any geographic-origin claim requires a laboratory opinion)" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.
Known uncertainty
- This entry's exact material identity is not fully settled.
- See “Disclosure and cautions” above
- Last reviewed
- 2026-09-01
Trade-name ruling
- Laboratory identification required before the name is used.
- Suggested listing name
- Opal (any geographic-origin claim requires a laboratory opinion)
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 Coober Pedy Opal, is set out in full under care on the Opal entry.
Care
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Treatments and identification leads
One row per treatment, with three standards side by side: how often it occurs and how stable it is (CIBJO), its category in GB/T 16552—2017 Table B.1 (this site's paraphrase) and how the JJA/AGL 2025 table lists it. Each CIBJO value links to its entry under “Testing and market”, where the wording and source are given in full.
This table scrolls sideways on narrow screens.
| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Dyeing | — | — | Treatment | — | — |
| Coating | — | — | Treatment | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: 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
Chinese standard nameThe national-standard name corresponding to Coober Pedy Opal is opal, but the name itself is not listed in the original, on the basis of GB/T 16552—2017. Trade and mineralogical namesCoober Pedy Opal is a trade name, not a mineralogical species name. Recommended listing nameThe suggested listing name is Opal (origin requires a laboratory opinion). Trade and mineralogical namesThe mineralogical name describes white opal or crystal opal historically associated with Coober Pedy in South Australia. Names in four languagesNames are given in Simplified Chinese, Traditional Chinese, English (Coober Pedy Opal) and Japanese (a katakana transliteration). Institution usageOn authority wording, the FTC and CIBJO texts on file have no wording for Coober Pedy Opal (checked), and GIA and Gem-A are unchecked; bodies without a recorded wording show the entry's own English name Coober Pedy Opal, which does not represent their position. Japanese namesThe entry's own Japanese name is the katakana transliteration, and Japan's GSJ wording for it is not yet verified by this site. Australia (GAA) writes Coober Pedy Opal and notes that it is a South Australian geographic indication.
- GSJ (Japan) formal name
- クーバーペディ・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 §5.1.1 c))
- Mineralogical name
- White or crystal opal historically associated with Coober Pedy, South Australia
Four-language names
- 简体中文
- 库伯佩迪欧泊
- 繁體中文
- 庫伯佩迪歐泊
- English
- Coober Pedy Opal
- 日本語
- クーバーペディ・オパール
National and regional formal names
- Australia (GAA)
- Coober Pedy Opal; South Australian geographic marker
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
- Natural amorphous gem material / mineraloid
- Mineral chemical class
- Not applicable
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
The treatments of Coober Pedy Opal are classified under the “Opal” row of GB/T 16552—2017 Annex B, Table B.1: filling, graded; dyeing, in the treatment category; coating, in the treatment category. The notes to Table B.1 and the definitions of the filling grades are on the Gem treatments page, and the full row, with the effect column, is on the Opal 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 structure, cleavage, birefringence, optical character, optical effects, density, refractive index and lustre of Coober Pedy Opal are taken from the cited clause for opal (the whole class), not measured separately. For opal (the whole class): structure amorphous, with no cleavage and no birefringence; optical character isotropic, with anomalous extinction often seen in fire opal; play-of-colour can occur; untreated, the quality factor (lustre) is vitreous to resinous. Mohs hardness 5–6.5; the cited clause covers the whole species, of which Coober Pedy Opal is only one variety. Density for opal (the whole class) is 1.25–2.23 g/cm³, derived from the clause value 2.15 and its permitted tolerance (+0.08, −0.90); refractive index for opal (the whole class) is 1.37–1.47, derived from the clause value 1.450 and its permitted tolerance (+0.020, −0.080); the clause has finer sub-ranges and the overall value is used.
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 Coober Pedy 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 Coober Pedy Opal (how to read class-level values).
Structure
Coober Pedy 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
Coober Pedy 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
Coober Pedy 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
Coober Pedy 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
- Qualification
The row we cite covers opal as a whole, and this entry is one of its varieties. The row states a property that holds for every piece alike — whether it dissolves, whether it cracks. That kind of property carries over to this entry. A numeric range such as hardness would not.
Source & check 2026-09-21
- Source
- Fact checked on
- 2026-09-21
Physical properties
Coober Pedy 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
Coober Pedy 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
Coober Pedy 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
Coober Pedy 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
Coober Pedy 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
Coober Pedy 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
Coober Pedy 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
- CIBJO definitions
- play of colour, chatoyancy
Quality factors
Coober Pedy 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 Coober Pedy 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
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
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.
- GIA – Gemological Institute of America (United States). Gem Encyclopedia.
- ICA – International Colored Gemstone Association.
- eCFR (United States). 16 CFR § 23.1 — Deception (general). In: 16 CFR Part 23 — Guides for the Jewelry, Precious Metals, and Pewter Industries.
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 (Coober Pedy Opal) is marked.
- Opal
Sub-entries (16)
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) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Coober Pedy 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. The entry exists so that buyers and sellers can check naming, disclosure and material facts item by item.