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Natural inorganic gem materials · Natural glass · Natural identity; treatment status unknown

Obsidian

Also known asSheen obsidian · Volcanic glass

Natural volcanic glass, an amorphous material rather than a mineral species; it should not be labelled “obsidian mineral”. 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.

Edited by JuneReviewed by RalphLast updated 2026-10-12Who maintains this page

FAQCare and wear

Questions people ask about Obsidian

Every sentence below is followed by the registered fact it rests on; answers add no new facts and promise no outcome.

Q1Obsidian is glass, so how is it different from man-made black glass?

Obsidian is glass produced by nature: silica-rich lava solidifies as glass with almost no crystallization as it cools, and it forms only in volcanic settings.NPS Hopewell Culture · Nature Communications (Llewellin et al., 2026) +1No synthetic counterpart of obsidian is commercially available.CIBJO Gemstone Book 2022According to the parent entry Natural Glass, natural glass shows its own diagnostic absorption bands in the mid-infrared.GB/T 16553—2017 (via parent entry Natural Glass (material))Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q2How does obsidian form?

Silica-rich magma rises from deep in the earth toward the surface.NPS Hopewell Culture · NPS Obsidian CliffThe magma erupts or flows onto the surface as lava.NPS Hopewell Culture · NPS Obsidian CliffAs it cools, the lava solidifies as natural volcanic glass with almost no crystallization; cooling must be fast enough to avoid crystallization yet slow enough for remnant bubbles to be resorbed, giving dense, almost bubble-free obsidian.NPS Hopewell Culture · NPS Obsidian Cliff +1A 2026 modelling study estimates that fully resorbing those bubbles takes at least a few days to a few decades, depending on the starting bubble content and the cooling rate.NPS Obsidian Cliff · Nature Communications (Llewellin et al., 2026) +1

Q3What causes the sheen in sheen or rainbow obsidian?

In fire obsidian from Glass Buttes, Oregon, thin layers about 300 to 700 nm thick filled with nano-size magnetite may cause thin-film interference and explain the rainbow colours.G&G Summer 2025 · G&G Spring 2017In Mexican obsidian, flow-flattened lens-shaped features filled with gas or glass of a different composition, together with aligned pyroxene or feldspar crystals, can produce a sheen from internal reflections.G&G Summer 2025 · G&G Spring 2017Studies of these volcanic glasses are extremely limited, and more than one mechanism may be involved.G&G Summer 2025 · G&G Spring 2017

Q4Is obsidian fragile, and can heat damage it?

Obsidian is a strong material, yet it can easily be shaped by chipping away flakes and honed to an exceptionally thin, sharp edge.NPS Hopewell Culture · NPS Obsidian CliffThe national standard gives a Mohs hardness of 5–6 for natural glass as a whole, tektite and volcanic glass alike, not a figure measured on obsidian itself.GB/T 16553—2017A US Forest Service review of burn tests notes that heated obsidian has been documented splitting, crazing, flaking and even breaking apart, with some of this damage appearing at fire-level peak temperatures of roughly 500–600 °C.USDA Forest Service RMRS-GTR-42 (Deal, 2012)

Q5Is obsidian a crystal or a mineral?

Neither: obsidian is a glass produced by nature and classed as an igneous rock.NPS Hopewell Culture · NPS Obsidian Cliff +2The national standard describes natural glass as amorphous, not crystalline.GB/T 16553—2017According to the parent entry Natural Glass, it is mainly SiO2 and may contain impurity elements.GB/T 16553—2017 (via parent entry Natural Glass (material))

Q6What does obsidian symbolize, and does it have healing powers?

There is no scientific evidence that obsidian has healing powers: the UK advertising regulators ASA and CAP state that they have not seen evidence that crystal therapy can treat medical conditions.ASA/CAP guidance (UK)Its recorded history is practical: toolmakers were already quarrying stone from Obsidian Cliff in Yellowstone more than 11,000 years ago.NPS Obsidian CliffMuseum objects include worked obsidian from the Cyclades dated to the 5th millennium BCE or later, and obsidian also appears in Minoan beads, Middle Kingdom Egypt and Mesoamerica.The Met 2013.1104.7a–d · The Met 2013.1104.5 +6

What this page can answer

This page covers

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

  • Obsidian (natural glass)
How obsidian forms: a schematic animation, not to scale; the captions are taken from the research record under “Material research” on this page.

If you reuse this animation, please credit LumaLark Wiki and link to this pageLicense: CC BY 4.0

Scene-by-scene transcript (8 scenes, with evidence grades and sources)

The caption of each scene in the animation above, with its evidence grade and sources.

  1. Scene 1What obsidian is

    Obsidian is glass produced by nature: silica-rich lava solidifies as glass with almost no crystallization as it cools, and it forms only in volcanic settings.

    Evidence grade B
    Sources
  2. Scene 2Where it forms: volcanic settings

    Volcanic settings in which silica-rich lava solidifies as glass with almost no crystal growth as it cools; most specimens the sources describe are black (the sources give no cause for the colour).

    Sources
  3. Scene 3Example path (1/3): silica-rich magma rises

    Silica-rich magma rises from deep in the earth toward the surface.

    Scope: The formation steps describe one example path, in which silica-rich lava reaches the surface and cools to obsidian; obsidian is also found in densely welded pyroclastic deposits, at the margins of shallow magmatic intrusions, and in blocks and pyroclasts produced by explosive eruptions.

    Sources
  4. Scene 4Example path (2/3): lava reaches the surface

    The magma erupts or flows onto the surface as lava.

    Sources
  5. Scene 5Example path (3/3): cooling, almost no crystallization, remnant bubbles resorbed

    The lava solidifies as natural volcanic glass (obsidian) with almost no crystallization as it cools; cooling must be fast enough to avoid crystallization yet slow enough for remnant bubbles to be resorbed, giving dense, almost bubble-free obsidian.

    Sources
  6. Scene 6Example path (3/3, cont.): how long until fully dense (model cases)

    In the study's model cases, lava starting with very few bubbles (about 3 percent by volume) and cooling no faster than about 10⁻³ °C/s can become fully dense in as little as a few days, whereas lava starting with about 50 percent bubbles by volume or more must cool no faster than about 10⁻⁷ °C/s and takes a few decades.

    Limitation noted in the record: the cooling rates and durations come from the models and experiments of one 2026 study and are general estimates, not specific to Obsidian Cliff or any other locality.

    Sources
  7. Scene 7Instance: Obsidian Cliff, Yellowstone

    At Obsidian Cliff in Yellowstone National Park the exposed vertical thickness reaches roughly 98 feet (30 m), in contrast to most obsidian, which appears as small rocks scattered among other formations.

    Sources
  8. Scene 8Colours of natural pieces

    Although typically jet black, obsidian — a glass formed in nature — may also appear brown, tan or green.

    Scope: This is a color and texture description only; the source gives no quantitative chemical composition.

    Evidence grade B
    Sources

In brief: Obsidian is a glass produced by nature and classed as an igneous rock, formed only in volcanic settings: silica-rich lava solidifies as glass with almost no crystallization as it cools.

Full research record (formation summary, 3 formation steps, link to appearance, timescale, related base materials, 2 supporting findings)

Obsidian is a glass produced by nature and classed as an igneous rock, formed only in volcanic settings: silica-rich lava solidifies as glass with almost no crystallization as it cools. The traditional explanation is that the lava cooled too quickly to crystallize; a 2026 study adds that cooling must be fast enough to avoid crystallization yet slow enough for remnant bubbles in the lava to be resorbed for dense, almost bubble-free obsidian to form. In the study's model cases, lava starting with very few bubbles (about 3 percent by volume) and cooling no faster than about 10⁻³ °C/s can become fully dense in as little as a few days, whereas lava starting with about 50 percent bubbles by volume or more must cool no faster than about 10⁻⁷ °C/s and takes a few decades. Obsidian is typically jet black, though brown, tan and green varieties also occur; at Obsidian Cliff in Yellowstone National Park the exposed vertical thickness is roughly 98 feet (30 m), and the obsidian there contains close to 0% crystals.

Scope: Covers natural volcanic glass formed as silica-rich lava solidifies with almost no crystallization; it forms only in places where there are volcanoes and does not form in non-volcanic areas. For example, the obsidian found at Hopewell sites in Ohio was brought there by people from distant volcanic areas. The formation steps describe one example path, in which silica-rich lava reaches the surface and cools to obsidian; obsidian is also found in densely welded pyroclastic deposits, at the margins of shallow magmatic intrusions, and in blocks and pyroclasts produced by explosive eruptions.

Sources NPS Hopewell Culture · NPS Obsidian Cliff · Nature Communications (Llewellin et al., 2026) +1
How it forms, step by step

  1. Silica-rich magma rises from deep in the earth toward the surface.

    Sources NPS Hopewell Culture · NPS Obsidian Cliff

  2. The magma erupts or flows onto the surface as lava.

    Sources NPS Hopewell Culture · NPS Obsidian Cliff

  3. The lava solidifies as natural volcanic glass (obsidian) with almost no crystallization as it cools; cooling must be fast enough to avoid crystallization yet slow enough for remnant bubbles to be resorbed, giving dense, almost bubble-free obsidian.

    Sources NPS Hopewell Culture · NPS Obsidian Cliff · Nature Communications (Llewellin et al., 2026)
Link to appearance

Obsidian is glassy, being jet black in color but also brown, tan, or green; it is a strong material, yet it can be easily shaped by chipping away flakes and honed to an exceptionally thin, sharp edge, and it was historically used for toolmaking.

Sources NPS Hopewell Culture · NPS Obsidian Cliff
Timescale

The cited National Park Service pages give no numeric age for obsidian formation; the USGS dates the eruption of the Obsidian Cliff flow to around 106,000 years ago (that flow only). The cliff was quarried more than 11,000 years ago, which is human use rather than formation time. A 2026 modelling study estimates that fully resorbing the remnant bubbles in cooling lava to form dense obsidian takes at least a few days to a few decades (depending on initial bubble content and cooling rate; resorption proceeds before the melt reaches the glass transition and stops thereafter) — the duration of the cooling process, not a formation date.

Sources NPS Obsidian Cliff · Nature Communications (Llewellin et al., 2026) · USGS Yellowstone Volcano Observatory
Related base materials
  • Silica-rich lava: Obsidian forms when lava solidifies as glass with almost no crystallization as it cools; lava is its direct precursor material
Supporting findings

Obsidian is glass produced by nature: silica-rich lava solidifies as glass with almost no crystallization as it cools, and it forms only in volcanic settings.

Evidence grade B

Scope: Rapid cooling that leaves no time to crystallize is the traditional popular explanation; a 2026 study finds that cooling must be fast enough to avoid crystallization yet slow enough for remnant bubbles to be resorbed for dense, almost bubble-free obsidian to form (the paper's abstract gives cooling on the order of 10⁻⁴–10⁻⁸ °C/s; the exact limit depends on the initial bubble content, and in the model case with very few initial bubbles (about 3 percent by volume) full resorption also occurs when cooling is no faster than about 10⁻³ °C/s).

Sources NPS Hopewell Culture · Nature Communications (Llewellin et al., 2026) · USGS Yellowstone Volcano Observatory

Obsidian occurs in volcanic areas where silica-rich magma cooled with almost no crystallization; at Yellowstone's Obsidian Cliff the exposed vertical thickness is about 98 feet (30 m).

Evidence grade B

Scope: The thickness figure describes one national-park locality and is not globally representative. The USGS describes the exposure as standing 150 to 200 ft above the surrounding ground surface; whether the two sources measure the same extent or use the same baseline has not been verified.

Sources NPS Obsidian Cliff · USGS Yellowstone Volcano Observatory

Recorded localities

Authoritative sources list the localities below; the list is not exhaustive.

Locality sketch mapLand outlines only; the map does not depict any national or regional boundary. Dots mark approximate positions. Base map: Natural Earth (public domain).

Europe

North America

  • Sevier Lake, Millard County, Utah, United StatesMineral specimen locality (not a source of jewellery material)
    Sources Mindat: Obsidian
  • Obsidian Cliff, Yellowstone National Park, Wyoming, United StatesHistorical sourceAncient source: main origin of obsidian at Midwestern sites, including Hopewell mortuary sites
    Sources NPS Obsidian Cliff

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

In fire obsidian from Glass Buttes, Oregon, thin layers about 300 to 700 nm thick filled with nano-size magnetite may cause thin-film interference and explain the rainbow colours; in Mexican obsidian, flow-flattened and aligned lenticular features filled with gas or glass of a different composition, together with oriented pyroxene or feldspar crystals, can produce a sheen from internal reflections (sometimes classed as aventurescence). Studies of these included volcanic glasses are extremely limited, and given the very different appearances of obsidian from different localities, more than one mechanism may be involved.

Evidence grade B

Scope: The source proposes thin-film interference only as a possibility and only for fire obsidian from a single locality (Glass Buttes); it cannot be extended to all rainbow obsidian, and the source notes that such studies are extremely limited. The explanation does not establish any sample's locality, naturalness, or treatment.

Sources G&G Summer 2025 · G&G Spring 2017

Human use and museum objects

Toolmakers were already quarrying stone from Obsidian Cliff more than 11,000 years ago.

Evidence grade B

Scope: This date records human quarrying and cannot serve as a formation date for the obsidian.

Sources NPS Obsidian Cliff

Museum evidence includes Cycladic worked obsidian fragments and a raw lump dated "5th millennium BCE or later" (Met 2013.1104.7a-d), recurring in Minoan beads (26.31.405, 26.31.254), Middle Kingdom Egypt (12.183.13a, b; Cleveland 1985.107) and Mesoamerica (Cleveland 1983.191; Met 1994.35.465).

Evidence grade A

Scope: Applies to collection objects recorded as obsidian (beads, blades, mirrors, vessels); individual volcanic-glass source descriptions follow the institutions' records.

Sources The Met 2013.1104.7a–d · The Met 2013.1104.5 · The Met 26.31.405 +5

The Met holds a group of worked obsidian fragments and a raw lump from the Cyclades dated to the 5th millennium BCE or later (acc. 2013.1104.7a-d) and a Cycladic obsidian blade of ca. 2700-2200 BCE (acc. 2013.1104.5), are examples of Aegean obsidian working. Minoan Crete left an obsidian bead in the form of a figure-of-eight shield (acc. 26.31.405, ca. 2200-1450 BCE) and an obsidian amulet (acc. 26.31.254, ca. 1650-1500 BCE). From Middle Kingdom Egypt come The Met's necklace of Hapiankhtifi with black obsidian ball beads and silver caps (acc. 12.183.13a, b, ca. 1981-1802 B.C., Middle Egypt) and a Cleveland Museum of Art obsidian cosmetic vessel of ca. 1859-1814 BCE (acc. 1985.107). In the Americas, Mixtec/Aztec ear ornaments in Cleveland (acc. 1983.191, ca. 1200-1519, Guerrero, Mexico) and Mexican obsidian blades in The Met (acc. 1994.35.465, before the 16th century) are examples of obsidian objects from Mesoamerica.

Sources The Met 2013.1104.7a–d · The Met 2013.1104.5 · The Met 26.31.405 +5

Scope: A museum object evidences only the existence and date of that artefact itself; it does not establish widespread ancient use of the material, nor does it attest the origin, naturalness, or treatment of any modern specimen. Cultural attributions follow the holding institution's records and are not extrapolated.

Objects cited

3000 BCE2000 BCE1000 BCE010002000Met 2013.1104.5ca. 2700–2200 BCEMet 26.31.405ca. 2200–1450 BCEMet 12.183.13a, bca. 1981–1802 B.C.CMA 1985.107c. 1859–1814 BCECMA 1983.191c. 1200–1519
Dates of museum objectsDates from the museums' open-access records (CC0); each bar spans the whole period named in the record, with qualifiers such as “early” or “possibly” kept in the label rather than turned into a narrower range; an arrow marks a record that reads “before” or “after” a yearSource: The Met / Cleveland Museum of Art open-access records
  • The Met 2013.1104.7a–dGroup of 3 worked obsidian fragments and a raw obsidian lump · 5th millennium or later · CycladicObsidian
  • The Met 2013.1104.5Obsidian blade · ca. 2700–2200 BCE · CycladicObsidian
  • The Met 26.31.405Obsidian bead in the form of of a figure-of-eight shield · ca. 2200–1450 BCE · MinoanObsidian
  • The Met 12.183.13a, bNecklace of Hapiankhtifi · ca. 1981–1802 B.C. · Middle EgyptBlack obsidian ball beads; silver caps Silver
  • Cleveland Museum of Art 1985.107Cosmetic Vessel (Beaker) · c. 1859–1814 BCE · Egypt, Middle Kingdom (2040–1648 BCE), Dynasty 12, reign of Amenemhat III (1860–1814 BCE)obsidian and gold
  • Cleveland Museum of Art 1983.191Pair of Ear Ornaments · c. 1200–1519 · Mexico, Guerrero, Ichcatiopan, Mixtec or Aztecobsidian, crystal

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • The National Park Service interpretive articles provide no numeric formation age or quantitative composition for obsidian; the cooling rates and durations come from the models and experiments of one 2026 study and are general estimates, not specific to Obsidian Cliff or any other locality.

Methodology

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
Obsidian

GB/T 16552—2017 Table A.2 “Obsidian”, 5.1.1 a), 5.1.2.2 a) · CIBJO Gemmological Laboratories Book 2024 §7.2.1.156 “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

Obsidian is Natural volcanic glass, not a mineral species; use "Obsidian" for listings, and disclose any known treatments.

What this means for you

Before buying, check the recommended listing name "Obsidian" 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

Care

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; per a study it cites, some (not all) of those kinds of damage appeared once peak temperatures reached roughly 500-600 °C, i.e. fire-level heat.

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.

QuestionMatching entries
Heat and thermal shocka 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; per a study it cites, some (not all) of those kinds of damage appeared once peak temperatures reached roughly 500-600 °C, i.e. fire-level heat

VerifyNames, standards, technical facts, clauses and sources

Names

Besides Obsidian, the name register records "Sheen obsidian" and "Volcanic glass", for which no restriction on use as a name is recorded (CIBJO Gemmological Laboratories Book 2024 §7.2.1.214 “Sheen obsidian”; CIBJO Gemstone Book 2022 Annex 8 “Sheen Obsidian”); 2 further names in non-Latin scripts are listed in the name register below (2 with no restriction recorded on use as a name).

Standard and listing namesGB/T 16552—2017 Table A.2 lists obsidian as a rock name, and the GB/T naming counterpart of Obsidian is Natural glass, the name itself not being listed in the standard; the suggested listing name is Obsidian. Obsidian is also known by a Chinese rock name, volcanic glass (conditionally applicable), Sheen obsidian and Volcanic glass. Candidate search termsOf these, the Chinese term for volcanic glass is a search candidate only, Sheen obsidian is an English narrower name (variety/subtype), and Volcanic glass is an English synonym. Names in four languagesThe four-language names are the Simplified and Traditional Chinese names, English Obsidian and the Japanese names, the Japanese form also being the GSJ (Japan) formal name; the mineralogical name is natural volcanic glass, not a mineral species. Institution usageCIBJO records Obsidian (CIBJO Gemmological Laboratories Book 2024); the FTC text on file has no wording for this name (checked); GIA and Gem-A are unchecked; bodies without a recorded wording show the English name of Obsidian, which does not represent their position. National standard namesGermany (RAL) and the European Union both use Obsidian.

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.

NameTypeMatchingUse as a nameBasis
no restriction recorded (4)
Sheen obsidianEnglishnarrower name (variety or subtype)matched automaticallyno restriction recordedCIBJO Gemmological Laboratories Book 2024 §7.2.1.214 “Sheen obsidian”; CIBJO Gemstone Book 2022 Annex 8 “Sheen Obsidian”
Volcanic glassEnglishsynonymmatched automaticallyno restriction recordededitorial ruling (no clause cited)
火山玻璃Simplified Chinesenarrower name (variety or subtype)search candidate onlyno restriction recordedGB/T 16553—2017 5.2.29
黑曜岩Simplified Chinesesynonymmatched automaticallyno restriction recordedGB/T 16552—2017 Table A.2 “Obsidian”

How each authority words this name: see Names › Authority wording.

Authority wording

GIA, FTC, CIBJO, Gem-A
Obsidian (on record for CIBJO (CIBJO Gemmological Laboratories Book 2024 §7.2.1.156); no wording for this name in the FTC text on file; GIA, Gem-A unchecked — bodies without a recorded wording show the entry's own English name)
GSJ (Japan) formal name
オブシディアン／黒曜石
GB/T naming counterpart (this name is not in the standard)
天然玻璃 (GB/T 16552—2017 Table A.2)
Mineralogical name
Natural volcanic glass, not a mineral species
Trade names and synonyms
Volcanic glass (synonym) · Sheen obsidian (narrower name (variety or subtype))

Four-language names

简体中文
黑曜石
繁體中文
黑曜石
English
Obsidian
日本語
オブシディアン／黒曜石

National and regional formal names

Germany (RAL)
Obsidian
European Union
Obsidian

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

Most material facts for Obsidian are taken by class. Registered for natural glass (the whole class): structure amorphous; cleavage none; optical character isotropic, with anomalous extinction common; birefringence none; Mohs hardness 5–6, covering tektites and volcanic glass, not measured on Obsidian alone; refractive index 1.48–1.51, derived from the clause value 1.490 and its permitted tolerance of +0.020/−0.010; the optical effect (cat's-eye effect) can occur but is rare; the quality factor (lustre) is vitreous, treatment status untreated. Registered for volcanic glass (obsidian, basaltic glass): density 2.3–2.5 g/cm³, derived from the clause value 2.40 and its permitted tolerance of ±0.10; body colour black (often with white spots), brown to brownish yellow, orange, red, and rarely green, blue or purplish red, treatment status untreated. Chemical composition, luminescence, spectra and magnification are written for natural glass (the whole class); see the Natural Glass 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 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 Obsidian (how to read class-level values).

Structure

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

Obsidian — Mohs hardness: 5–6

GB/T 16553—2017

123456789105–6References (diamond = value, bar = range; below)

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))

Mohs hardnessSource: GB/T 16553—2017
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

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

Physical properties

Obsidian — density: 2.3–2.5 g/cm³

GB/T 16553—2017

0.51.52.53.54.55.56.57.52.3–2.5
Specific gravitySource: GB/T 16553—2017
Does this standard apply
applies to this entry
What this covers
volcanic glass (obsidian and basalt glass)
Qualification

The clause we cite gives 2.40, with a stated tolerance of ±0.10. The range shown here is worked out from that.

Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 Density · Volcanic glass (locator checked 2026-09-28)
Fact checked on
2026-09-26

Optical

Optical effects on record: chatoyancyrepresentative example: cause in Tiger’s Eye (schematic)

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

Obsidian — refractive index: 1.48–1.51

GB/T 16553—2017

1.31.72.12.52.93.31.48–1.51
Refractive indexSource: 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

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

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

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

Obsidian — body colour: black (commonly with white streaks), brown to brownish yellow, orange, red; green, blue and purplish red are uncommon; obsidian commonly has white patches, sometimes in a chrysanthemum-like pattern.

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
What this covers
volcanic glass (obsidian and basalt glass)
Qualification

In chapter 5 of GB/T 16553—2017, the colour entries of Fei Cui / Jadeite Jade, Silicified Jade, Garnet and other variety clauses also name black or a blackish colour.

General note
colour alone is not identity
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.29 Colour · Volcanic glass (locator checked 2026-09-28)
Fact checked on
2026-09-26
CIBJO definitions
chatoyancy

Quality factors

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.

1.481.51.521.542.22.32.42.52.6Refractive indexSpecific gravity12345Obsidian

This material (RI / SG midpoints): 1.495 / 2.4; Closest values: 1Haüyne 1.5 / 2.46, 2Hackmanite 1.483 / 2.27, 3Apophyllite 1.536 / 2.4, 4Chrysocolla 1.516 / 2.2, 5Serpentine 1.532 / 2.62

Show the full chart (330 registered materials)1.41.51.61.71.81.922.12.22.32.41234567Refractive indexSpecific gravity12345Obsidian

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

Refractive index × specific gravity (all registered materials)Each dot is one material's registered refractive index and specific gravity (range midpoints, not measurements); gold = this material, dark = the nearest few (picked on this site by distance in RI ÷ 0.02 and SG ÷ 0.1, leaving out near-identical varieties of the same species)Source: each material's registered refractive index and specific gravity facts (GB/T 16553 and others; sources on each entry)

Testing and market

Which tests CIBJO's laboratory rules require for Obsidian, and what each method means, are shown in the rules table on the laboratory testing page; CIBJO's laboratory rules call for particular checks on obsidian for man-made glass. There is no synthetic obsidian on the market.

The tests the CIBJO laboratory protocol requires for this material, and what each method means, are in the protocol table on the laboratory testing page: §6.1.55.

How far testing can go

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

Obsidian — what the CIBJO laboratory protocol says to watch for: artificial glass

CIBJO Gemmological Laboratories Book 2024

Treatment state
any treatment state
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Each row's “Source & check” expands to the full source; the date beside it is the fact check date.

Clause-level definitions

Obsidian has a clause-level definition in CIBJO Gemmological Laboratories Book 2024 under the term Obsidian, as a volcanic natural glass formed as an extrusive igneous rock; the cross-check shows it is defined directly by CIBJO and also appears in the GB/T annex. CIBJO Gemmological Laboratories Book 2024 also defines the term Sheen obsidian, as showing a whitish (silvery) or yellowish (golden) looking sheen; the cross-check shows it is defined directly by CIBJO, and no identically named English entry was found in this edition of the GB/T annex.

This table scrolls sideways on narrow screens.

TermClauseDefinitionCross-check
Obsidian7.2.1.156Obsidian is a volcanic natural glass, formed as an extrusive igneous rock. The lava extruded from a volcano cooled rapidly, causing minimal crystal growthDefined directly by CIBJO; also present in the GB/T annex.
Sheen obsidian7.2.1.214Sheen obsidian shows a whitish (‘silvery’) or yellowish (‘golden’) looking sheenDefined 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

GB/T 16552—2017
Listed Table A.2 “Obsidian” · Source
GB/T 16552—2017
Naming rule 5.1.1 a) · Source
GB/T 16552—2017
Naming rule 5.1.2.2 a) · Source
CIBJO Gemmological Laboratories Book 2024
Listed §7.2.1.156 “Obsidian” · Source

Sources

Further reading

Related intention themes

These reviewed links connect this material with LumaLark intention themes. Each label identifies whether the link is a brand interpretation or a historical and cultural record; neither describes an effect or outcome of the material.

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 (Obsidian) is marked.

This table scrolls sideways on narrow screens.

PageContentStatus
Browsing familyNatural glassLive
Related articlesTo be added (placeholder)Planned

Who maintains this page

The material facts in the 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.

Facts editor
June
Reviewer
Ralph
How facts are checked
Each fact is matched to the clause it cites; facts checked between 2026-09-20 and 2026-10-06
Last revised
2026-10-12
Purpose
Lets buyers and sellers check naming, disclosure and material facts clause by clause.

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