On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Natural glass · Natural identity; treatment status unknown
Rainbow Obsidian
A commercial optical name for Obsidian showing a rainbow-like iridescent sheen; the sheen describes appearance and is not a separate mineral species. 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 Rainbow Obsidian 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 Rainbow ObsidianHow far lab testing can go and whether a synthetic exists
- Caring for and wearing Rainbow ObsidianCleaning, heat, chemicals and light, as the cited sources give them
- Hardness and refractive index of Rainbow ObsidianEach value with its source and check date
- Rainbow Obsidian 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 Rainbow ObsidianThe listing name to use; what must be disclosed before sale
- Standard clauses that define Rainbow ObsidianWhich 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
Rainbow obsidian is obsidian showing an iridescent sheen; its parent material is obsidian, a natural volcanic glass formed when silica-rich magma cools too fast to crystallize, occurring only in volcanic regions. The iridescence can be produced by thin-film interference in internal thin layers (e.g. 300–700 nm layers filled with nano-sized magnetite crystals); mechanisms may differ by locality.
Scope: Covers an overview of the formation of rainbow obsidian; formation content follows that of the parent material obsidian, and the iridescence mechanism is covered in the optical effects entry.
Sources NPS Hopewell Culture · NPS Obsidian Cliff · CIBJO Gemstone Book 2022 +1
Where it forms
Volcanic regions where silica-rich (rhyolitic/dacitic) magma cools rapidly.
Sources NPS Hopewell Culture · NPS Obsidian Cliff
The parent obsidian is a glassy natural glass, black but also brown, tan, or green.
Sources NPS Hopewell Culture · NPS Obsidian Cliff
How it forms, step by step
Silica-rich magma rises to the surface and cools rapidly.
Sources NPS Hopewell Culture · NPS Obsidian Cliff
Cooling is too fast for atoms to arrange as crystals, producing amorphous volcanic glass.
Sources NPS Hopewell Culture · NPS Obsidian Cliff
During solidification, aligned micro-inclusions/thin layers are preserved inside, giving the sheen/iridescent appearance.
Sources NPS Hopewell Culture · NPS Obsidian Cliff
Link to appearance
An appearance-based name ('sheen') describes an optical effect and cannot alone establish identity, naturalness, treatment, or origin.
Sources CIBJO Gemstone Book 2022 · G&G Summer 2025
Timescale
The sources in this record give no absolute age or growth duration for this variety.
Sources NPS Hopewell Culture · NPS Obsidian Cliff
Related base materials
- obsidian: Obsidian is the parent material of this name; this name is an occurrence/optical variety name, not a separate material
Supporting findings
Obsidian is a natural volcanic glass (a glassy igneous rock) formed when silica-rich magma cools so rapidly that it does not crystallize, so it occurs only where there is volcanic activity.
Evidence grade AScope: Applies to the natural origin of obsidian (the parent material); it states rapid cooling, not a specific eruption age.
Sources NPS Obsidian Cliff · NPS Hopewell Culture
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
North America
- La Revoltosa Mine, San Andreas, Magdalena, Jalisco, Mexico
Sources Mindat: Rainbow Obsidian
- Glass Buttes, Lake County, Oregon, United States
Sources G&G Summer 2025 · Mindat: Rainbow Obsidian
- Davis Creek, Modoc County, California, United States
Sources Mindat: Rainbow Obsidian
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 name refers to a variety of obsidian (parent material obsidian) whose appearance arises from reflection off internal aligned inclusions.
Evidence grade AScope: Describes the optical mechanism (reflection from aligned inclusions, sometimes aventurescence); does not claim it is an independent material.
Other research findings
In CIBJO gemmological nomenclature, obsidian is listed as a 'natural glass', an amorphous natural gem material rather than a mineral species.
Evidence grade AScope: Defines the material class of obsidian (natural glass); not a specific variety.
Sources CIBJO Gemstone Book 2022
Studies of these aligned-inclusion/thin-layer sheens in obsidian are still limited, and sheen obsidians from different localities differ markedly, so multiple mechanisms may be involved.
Evidence grade AScope: Acknowledges limited evidence; does not claim one mechanism explains all golden/silver sheen obsidian.
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The sources give no single mechanism for all rainbow obsidian and note that mechanisms may differ by locality.
- Obsidian is a natural glass, not a mineral species; the variety name describes appearance only and is not a determinable material.
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
- Rainbow Obsidian
GB/T 16552—2017 5.1.1 c), 5.3.4 · CIBJO Gemmological Laboratories Book 2024 §7.2.1.192 “Rainbow obsidian”
Construction or treatment status
Natural identity; treatment status unknown
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
"Rainbow Obsidian" is a market name rather than a mineral species name; before using it, verify: Industry-wide term that does not denote a single species.
What this means for you
Before buying, check the recommended listing name "Rainbow Obsidian" 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
- Industry-wide term that does not denote a single species.
- Suggested listing name
- Rainbow Obsidian
Care and wear
Care
Rainbow Obsidian — care (heat): a US Forest Service review of burn tests notes that heated obsidian has been documented splitting, crazing, flaking and even breaking apart; the same report says the temperature at which obsidian is altered depends on both how hot it gets and how long the heat lasts.
USDA Forest Service RMRS-GTR-42 (Deal, 2012)
- Treatment state
- any treatment state
Source & check 2026-10-06
- Source
- Fact checked on
- 2026-10-06
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
Each question links to the matching entries on this page; whether they answer it fully, go by the entry wording.
This table scrolls sideways on narrow screens.
VerifyNames, standards, technical facts, clauses and sources
Names
Besides Rainbow Obsidian, the name register records "Rainbow obsidian", for which no restriction on use as a name is recorded.
Trade and mineralogical namesRainbow Obsidian is a trade name or synonym, written in English as Rainbow obsidian; the mineralogical name is paraphrased as obsidian with an iridescent sheen. Standard and listing namesThe full text of GB/T 16552—2017 does not contain Rainbow Obsidian, and the GB/T naming counterpart is natural glass (GB/T 16552—2017 Table A.2). The suggested listing name is Rainbow Obsidian. Names in four languagesNames are given in Simplified Chinese, Traditional Chinese, English (Rainbow Obsidian) and Japanese; the Japanese name is the entry's own, and the GSJ (Japan) wording for Rainbow Obsidian is not yet verified by this site. Trade and mineralogical namesThe English Rainbow Obsidian is registered as an English market name. Institution usageOn authority wording, the CIBJO Gemmological Laboratories Book 2024 records Rainbow Obsidian; checking shows that the FTC text on file does not use Rainbow Obsidian; GIA and Gem-A are unchecked. Bodies without a recorded wording show the entry's own English name, which does not represent the position of the bodies concerned.
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) | ||||
| Rainbow obsidianEnglish | market name | matched automatically | no restriction recorded | editorial ruling (no clause cited) |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- レインボーオブシディアン (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)
- 天然玻璃 (GB/T 16552—2017 Table A.2)
- Mineralogical name
- Obsidian with iridescent sheen
Four-language names
- 简体中文
- 彩虹黑曜石
- 繁體中文
- 彩虹黑曜石
- English
- Rainbow Obsidian
- 日本語
- レインボーオブシディアン
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural inorganic gem materials
- Browsing family
- Natural glass
- Identity tier
- Natural glass
- Mineral chemical class
- Not applicable
- Construction or treatment status
- Natural identity; treatment status unknown
What it is and how it's identified
The structure, Mohs hardness, cleavage, optical character, refractive index, birefringence, pleochroism, lustre and cat's-eye effect of Rainbow Obsidian are taken from natural glass as a whole category, not data measured on rainbow obsidian alone. For natural glass as a whole category: amorphous structure, no cleavage, optically isotropic and commonly with anomalous extinction, no birefringence; Mohs hardness 5–6 is the range for the whole natural glass category, not data measured on rainbow obsidian; the refractive index of 1.48–1.51 is derived from the cited clause value of 1.490 with an allowed deviation of +0.020/−0.010. For natural glass as a whole category, when untreated there is no pleochroism and the quality factor lustre is vitreous; a cat's-eye effect may be seen but is rare. The iridescence effect is registered as iridescence according to the CIBJO Rainbow obsidian entry.
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 natural glass (whole class), so they are not repeated on the Rainbow Obsidian page; see the material facts on the Natural Glass (material) entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Rainbow Obsidian (how to read class-level values).
Structure
Rainbow Obsidian — structure (overall): amorphous (not crystalline)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural glass (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Rainbow Obsidian — Mohs hardness: 5–6
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
- What this covers
- natural glass (whole class)
- Qualification
This is the range for the whole class, not a measured value for this variety. The clause covers all natural glass (tektite and volcanic glass).
Source & check 2026-09-20
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (locator checked 2026-09-20)
- Fact checked on
- 2026-09-20
Rainbow Obsidian — cleavage: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural glass (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Rainbow Obsidian — optic character: isotropic, usually with anomalous extinction
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural glass (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Rainbow Obsidian — refractive index: 1.48–1.51
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural glass (whole class)
- Qualification
The clause we cite gives 1.490, with a stated tolerance of +0.020 / -0.010. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Rainbow Obsidian — birefringence: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural glass (whole class)
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Rainbow Obsidian — pleochroism: none
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- natural glass (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Rainbow Obsidian — optical effect (iridescence): iridescent.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Rainbow Obsidian — optical effect (chatoyancy): seen; rare
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- natural glass (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
- CIBJO definitions
- chatoyancy
Quality factors
Rainbow Obsidian — quality factor (lustre): vitreous
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- natural glass (whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 (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.
Testing and market
No synthetic counterpart of Rainbow Obsidian is available on the market, as recorded in the CIBJO 2022 Gemstone Book (The Gemstone Book). The CIBJO laboratory protocol places Rainbow Obsidian under Obsidian; its identification is in the identification section of the Obsidian entry, and the list of required methods is on the laboratory testing page.
The CIBJO laboratory protocol covers Rainbow Obsidian under “Obsidian” (§6.1.55): see identification on the Obsidian entry; the required tests are listed on the CIBJO laboratory protocol table for Obsidian.
How far testing can go
Rainbow Obsidian — 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
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Clause-level definitions
Rainbow Obsidian is defined directly in CIBJO Gemmological Laboratories Book 2024, listed under the entry name Rainbow obsidian, with the definition being obsidian with iridescent colours, that is, obsidian showing rainbow-like iridescence in appearance. The cross-check result for this definition is that it is defined directly by CIBJO and no identically named English entry was found in this edition of the GB/T annex, so the clause-level definition of Rainbow Obsidian rests on CIBJO Gemmological Laboratories Book 2024.
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Rainbow obsidian | 7.2.1.192 | Obsidian with iridescent colours | 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
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 Natural Glass (material) on this site: 7 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Rainbow Obsidian) is marked.
- Natural Glass (material)
Sub-entries (6)
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Natural glass | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Rainbow Obsidian 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.