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Natural inorganic gem materials · Mineral species · Natural identity; treatment status unknown

Corundum

The aluminium oxide mineral species with the formula Al2O3; Ruby and Sapphire are both gem varieties of it. 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 RalphReviewed by JuneLast updated 2026-10-12Who maintains this page

FAQCare and wear

Questions people ask about Corundum

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

Q1Why does corundum come in so many colours, from ruby red to sapphire blue?

Pure corundum (Al2O3) is colourless; the colour of natural corundum comes from six main chromophores, for example Cr3+ giving pink to red and the Fe2+-Ti⁴⁺ pair giving blue.G&G Spring 2020Fe3+ gives yellow and V3+ gives colour change, so one mineral species shows colours from pigeon's-blood red to every fancy sapphire hue.G&G Spring 2020CIBJO's Gemmological Laboratories Blue Book lists colour change among corundum's optical effects.CIBJO Gemmological Laboratories Book 2024

Q2Is there synthetic corundum, and can you tell it from natural corundum by eye?

Yes, synthetic corundum is commercially available.CIBJO Gemstone Book 2022Corundum materials can be confused by colour, sometimes even mistaken for other gems, and appearance plus a single measurement is not always enough.G&G Fall 2019Laboratories combine several tools: microscopy to spot coatings or fillings, infrared, UV-visible-near-infrared and Raman spectroscopy to confirm the phase and absorption features, and EDXRF to identify coating elements.G&G Fall 2019Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.What this page can answer

Q3Is corundum durable enough to wear every day?

Yes: GIA rates corundum (ruby and sapphire) at Mohs 9 and describes it as tough with no cleavage, suiting rings worn daily.GIA Gem Encyclopedia (care guide)GIA adds that corundum holds up in ordinary wear and is generally unaffected by heat, light or everyday chemicals.GIA Gem Encyclopedia (care guide)Filled corundum is a separate case: CIBJO's Gemstone Book rates the filling treatment of corundum as unstable.CIBJO Gemstone Book 2022

Q4What do 'heating', 'NH' and 'diffusion' mean on a corundum report?

In the standard report wording of the LMHC, 'indications of heating' (abbreviated H) means the stone was heated to change its colour or transparency.LMHC Information Sheet #7'No indications of heating' (NH) means no signs of heating were seen.LMHC Information Sheet #7'(Lattice) diffusion' means the colour was created or changed by an element, such as beryllium, diffused into the crystal from outside during heating.LMHC Information Sheet #2

Q5What is glass-filled corundum, and does it need special care?

CIBJO's Gemstone Book records filling of corundum as common.CIBJO Gemstone Book 2022A report line saying 'glass filled fissures' means glass was put into fissures and cavities to improve clarity; the stone is still natural corundum, and the extent is graded separately.LMHC Information Sheet #3GIA says fracture-filled, cavity-filled or dyed corundum should be cleaned with nothing more than a damp cloth.GIA Gem Encyclopedia (care guide)

Q6How does corundum form?

Natural corundum deposits are either primary or secondary: primary deposits are magmatic or metamorphic, and secondary deposits are present-day placers.G&G Winter 2019In magmatic settings corundum crystallizes directly from silica-deficient melts; in metamorphic settings it forms from alumina-rich rocks at about 500–800°C.G&G Winter 2019Placers form when the host rock weathers and the chemically durable corundum grains are carried, sorted and concentrated.G&G Winter 2019Corundum itself cannot be dated directly; its ages are obtained indirectly from minerals that formed with it.G&G Winter 2019

Q7What makes good-quality star corundum, such as star sapphire and star ruby?

According to GIA, the best star corundum shows a crisp, distinct star against strongly saturated colour.GIA Sapphire Quality FactorsThe most prized colours are the same as in corundum without a star: red and blue.GIA Sapphire Quality Factors

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

Corundum is the independent mineral species with the formula Al2O3, formed by natural geological processes. Gem corundum deposits are divided into primary and secondary. Primary deposits are of two types by geological environment: magmatic—corundum crystallized directly from silica-deficient melts (e.g., syenite, nepheline syenite) or carried to the surface as xenocrysts/megacrysts in alkali basalt and lamprophyre—and metamorphic, in which corundum forms by metamorphism of alumina-rich rocks under amphibolite–granulite facies conditions (about 500–800°C), together with metamorphic-metasomatic deposits (desilicated pegmatite/plumasite, skarn, shear zone). Secondary deposits are present-day placers formed by erosion, transport and concentration of primary corundum. Pure corundum is colourless; colour comes from trace chromophores in the lattice.

Scope: Covers the general definition of natural corundum as a distinct mineral and the origin of its primary/secondary deposits; does not address trade naming for any particular locality or colour variety, nor treatment and synthesis.

Sources G&G Winter 2019 · G&G Spring 2020 · G&G Spring 2015

Where it forms

Magmatic setting: corundum crystallizes directly from silica-deficient melts (syenite, nepheline syenite), or is carried to the surface as xenocrysts/megacrysts in alkali basalt and lamprophyre magmas.

Sources G&G Winter 2019

Metamorphic setting: alumina-rich carbonates (marble), mafic–ultramafic rocks (M-UMR), gneiss and quartzite recrystallize to corundum under amphibolite–granulite facies conditions (about 500–800°C) during regional or contact metamorphism.

Sources G&G Winter 2019

Metamorphic-metasomatic setting: at contacts between granitic/pegmatitic and mafic–ultramafic or marble rocks, desilication and fluid metasomatism produce plumasite, skarn and shear-zone corundum.

Sources G&G Spring 2015

Secondary placer setting: erosion of primary deposits concentrates corundum in eluvial, colluvial and alluvial placers along slopes and rivers.

Sources G&G Winter 2019

How it forms, step by step

  1. Direct magmatic crystallization: in silica-deficient alkaline magmas, corundum crystallizes from the melt as an accessory phase, or is entrained as a xenocryst by rising magma.

    Sources G&G Winter 2019

  2. Metamorphic and metasomatic crystallization: alumina-rich rocks metamorphose to corundum under amphibolite–granulite facies; at contacts, desilication—Si diffusing from pegmatite into ultramafic rock—raises the Al:Si ratio and precipitates corundum.

    Sources G&G Spring 2015 · G&G Winter 2019

  3. Weathering, erosion and placer concentration: corundum-bearing host rock breaks down, and the chemically durable corundum grains are transported, sorted and concentrated into secondary deposits.

    Sources G&G Winter 2019

Link to appearance

Pure corundum (Al2O3) is colourless; the colours of natural corundum come from trace chromophores in the lattice (e.g., Cr3+ for pink/red, the Fe2+-Ti⁴⁺ pair for blue, Fe3+ for yellow, V3+ for colour change), so one mineral species shows colours from pigeon’s-blood red to every fancy sapphire hue.

Sources G&G Spring 2020

Timescale

Corundum formation worldwide is grouped into four periods: the Archean (about 2.97–2.6 Ga, e.g. southwest Greenland), the Pan-African orogeny (about 750–450 Ma), the Cenozoic Himalayan orogeny (about 45–5 Ma), and Cenozoic alkali-basalt volcanism (65 Ma to Quaternary). Corundum itself cannot be dated directly; ages come from indirect dating of coeval minerals (zircon, monazite, rutile, micas).

Sources G&G Winter 2019

Supporting findings

Natural corundum deposits are divided into primary and secondary; primary deposits are subdivided by geological environment into magmatic and metamorphic types, while secondary deposits are present-day placers.

Evidence grade A

Scope: The standard classification of natural gem corundum deposits; it does not cover the genesis detail of any single deposit.

Sources G&G Winter 2019

Corundum forms in magmatic settings by direct crystallization from silica-deficient melts and in metamorphic settings by metamorphism of alumina-rich rocks under amphibolite–granulite facies at about 500–800°C; desilication metasomatism at contacts (plumasite, etc.) also produces corundum.

Evidence grade A

Scope: The 500–800°C range summarizes metamorphic formation; individual deposits may differ in P–T conditions.

Sources G&G Winter 2019

Corundum only forms within a narrow window of pressure and temperature and where aluminium, chromium and oxygen are sufficiently available; ruby at Montepuez, Mozambique, for instance, formed chiefly through metasomatism, when a magma-derived fluid interacted with low-silica host rocks that had seen amphibolite-grade metamorphism (roughly 0.4–1.1 GPa, 550–750°C).

Evidence grade A

Scope: The P–T values are an example from Montepuez and are not representative of all corundum deposits.

Sources G&G Spring 2015

Corundum formation is grouped into four periods: the Archean about 2.97–2.6 Ga, the Pan-African orogeny about 750–450 Ma, the Himalayan about 45–5 Ma, and Cenozoic alkali-basalt volcanism 65 Ma to Quaternary; because no suitable geochronometer exists, corundum ages are obtained indirectly from coeval minerals.

Evidence grade A

Scope: The four periods are a global synthesis; individual deposits may span periods or correspond differently.

Sources G&G Winter 2019

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).

Africa

Asia

North America

Oceania

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

Pure corundum (Al2O3) is colourless; colour in natural corundum is caused by six major chromophores—Cr3+, h•-Cr³⁺, Fe3+, h•-Fe³⁺, Fe2+-Ti⁴⁺ and V3+—for example Cr3+ giving pink-red and the Fe2+-Ti⁴⁺ pair giving blue.

Evidence grade A

Scope: A summary of the main chromophores in natural corundum from quantitative absorption spectroscopy; not the full chromophore mix of every colour variety.

Sources G&G Spring 2020

How it is identified

Corundum materials can be confused by colour, sometimes mistaken even for other gems, and appearance plus a single measurement is not always enough. A laboratory uses several tools with distinct roles: microscopy to spot coatings or fillings, Fourier-transform infrared, ultraviolet/visible/near-infrared and laser Raman spectroscopy to confirm the phase and absorption features, and energy-dispersive X-ray fluorescence to identify coating elements. Such testing should be carried out by an accredited laboratory.

Evidence grade A

Scope: Corundum identification and treatment judgement are done in a laboratory by an accredited body; no operational thresholds are given.

Sources G&G Fall 2019

Corundum, both ruby and sapphire, is often priced on locality, with goods traded under names such as Kashmir, Burma, Ceylon, Mozambique or Madagascar. A locality name, however, is only a trade attribution and is not a determined origin. Origin work is a laboratory exercise: the deposit type is addressed first, then inclusion suites and trace-element suites (measured by methods such as laser ablation ICP-MS) are compared with reference databases for known localities to yield a conclusion of consistency or inconsistency with a source. Because the characteristic ranges of different localities overlap and vary within a single deposit, the conclusion is probabilistic and may be only inconclusive; heating, filling and diffusion alter the measurable features and must be excluded first. Origin cannot be inferred from appearance or name; an origin conclusion must be issued by a qualified laboratory for a specific specimen. This entry offers no self-test criteria or thresholds.

Evidence grade A

Scope: Origin cannot be inferred from appearance or name; an origin conclusion must be issued by a qualified laboratory for a specific specimen, and this entry provides no self-test criteria or thresholds.

Sources G&G Winter 2019 · G&G Summer 1998 · G&G Spring 2015 +1

Other research findings

For star corundum (star sapphire and star ruby), the best stones show a crisp, distinct star against strongly saturated colour, and the most prized colours are the same as in non-phenomenal corundum: red and blue.

Evidence grade B

Scope: Covers star corundum as described in one educational source's sapphire quality page; colour and clarity factors for faceted ruby and sapphire are given on those entries. Not a grading standard and not a statement about the value of any piece.

Sources GIA Sapphire Quality Factors

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • The genetic classification and P–T data come from GIA Gems & Gemology reviews and research papers—laboratory/geological conclusions, not origin determinations for any specific trade parcel.
  • Corundum cannot be dated directly; the four formation periods rest on indirect ages from coeval minerals and carry uncertainty.

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
Corundum

GB/T 16552—2017 Table A.1 “Corundum” · IMA Mineral List 2026-07 “Corundum”

Construction or treatment status

Natural identity; treatment status unknown

Treatments recorded for this material: Heated / Heat-treated, Dyed (via parent material), Filled / Fracture-filled (via parent material), Diffusion-treated (via parent material), Irradiated (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

Corundum is often subjected to heating. Under GB/T 16552-2017, heating counts as an optimization, so the plain gem name may be used (§5.4.2.1 a). Do not assume it is unenhanced.

Evidence

  • GB/T · Table A.1, row 刚玉 (Corundum)

What this means for you

Before buying, check the recommended listing name "Corundum" 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

Corundum — care (cleaning): GIA considers ultrasonic and steam cleaning usually safe for corundum that is untreated, heated, or lattice-diffused; for corundum that is fracture-filled, cavity-filled or dyed, GIA says to clean it with nothing more than a damp cloth.

GIA Gem Encyclopedia (care guide)

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

Corundum — care (chemicals): GIA warns that boric acid powder can etch the surface of corundum, untreated stones included.

GIA Gem Encyclopedia (care guide)

Treatment state
any treatment state
Source & check 2026-10-06
Source
Fact checked on
2026-10-06

Corundum — care (wear): According to GIA, corundum holds up in ordinary wear and is generally unaffected by heat, light or everyday chemicals; gIA rates corundum (ruby and sapphire) at Mohs 9 and describes it as tough with no cleavage, suiting rings worn daily.

GIA Gem Encyclopedia (care guide)

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
Can it go in an ultrasonic or steam cleaner?GIA considers ultrasonic and steam cleaning usually safe for corundum that is untreated, heated, or lattice-diffused; for corundum that is fracture-filled, cavity-filled or dyed, GIA says to clean it with nothing more than a damp cloth
Contact with acids, alkalis and household chemicalsGIA warns that boric acid powder can etch the surface of corundum, untreated stones included
Wearing limits (knocks, settings)According to GIA, corundum holds up in ordinary wear and is generally unaffected by heat, light or everyday chemicals; gIA rates corundum (ruby and sapphire) at Mohs 9 and describes it as tough with no cleavage, suiting rings worn daily

Treatments and identification leads

Values not givenThe registered treatment for Corundum is filling, with the status treated, stability unstable and prevalence common; the identification leads and source are both “—”, meaning the cited source gives no value, not “none”. SyntheticsAccording to the registered entries, synthetic Corundum is on the market.

This table scrolls sideways on narrow screens.

TreatmentMarket frequency (CIBJO)Stability (CIBJO)GB/T 16552 categoryJJA/AGL listingIdentification leads
fillingStatus: treatedcommonlyunstable———

Where each treatment acts (schematics): Filled / Fracture-filled

“—” means the cited source gives no value for that item, not “none”. Source: CIBJO Gemstone Book 2022

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

How lab reports word it

Further LMHC wording for this material (identification line, treatment wording, extent grades, durability note) is not itemised on this page; see LMHC information sheet #1, LMHC information sheet #2, LMHC information sheet #3 and the LMHC index on the laboratory testing page.

how lab reports word it (treatment wording)3 sources compared

Corundum — how lab reports word it (treatment wording): This line means the colour was created or changed by an element diffused into the crystal from outside during heating (beryllium, for example); the element is named when known.

LMHC Information Sheet #2

Wording on the report: (lattice) diffusion of (a) chemical element(s)

Case
heated with an element diffused in from outside
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Corundum — how lab reports word it (treatment wording): This line means glass was put into fissures and cavities to improve clarity; the stone is still natural corundum, and the extent is graded separately.

LMHC Information Sheet #3

Wording on the report: glass filled fissures or glass in fissures and cavities

Case
glass-filled fissures and cavities
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Corundum — how lab reports word it (treatment wording): This line (abbreviated H) means the stone was heated to change its colour or transparency; the bracketed part is optional.

LMHC Information Sheet #7

Wording on the report: Indications of heating (to modify the colour or transparency of the stone)

Case
indications of heating
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

Corundum — how lab reports word it (treatment wording): This line (abbreviated NH) means no signs of heating were seen

LMHC Information Sheet #7

Wording on the report: no indications of heating (NH)

Case
no indications of heating
Source & check 2026-09-26
Source
Fact checked on
2026-09-26

VerifyNames, standards, technical facts, clauses and sources

Names

Standard and listing namesThe Chinese formal name of Corundum comes from GB/T 16552—2017 Table A.1; the suggested listing name is likewise Corundum, based on the “Corundum” entry in GB/T 16552—2017 Table A.1 and “Corundum” in the IMA mineral list 2026-07. Trade and mineralogical namesThe mineralogical name is Corundum (Al2O3). Japanese namesThe GSJ (Japan) formal name is written in kanji with a katakana reading. Names in four languagesThe four-language names are the Simplified and Traditional Chinese names, English Corundum and the Japanese names. Institution usageFor authority wording, CIBJO records Corundum (CIBJO Gemmological Laboratories Book 2024); the FTC text on file has no wording for this name (checked); GIA and Gem-A are unchecked, and bodies without a recorded wording show the entry's own English name, which does not represent their position.

Authority wording

GIA, FTC, CIBJO, Gem-A
Corundum (on record for CIBJO (CIBJO Gemmological Laboratories Book 2024); 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
鋼玉（コランダム）
Chinese formal name
刚玉 (GB/T 16552—2017 Table A.1)
Mineralogical name
Corundum (Al2O3)

Four-language names

简体中文
刚玉
繁體中文
剛玉
English
Corundum
日本語
コランダム／鋼玉

See also: Misleading and prohibited trade names · Supplementary name index

Classification

Origin
Natural materials
Material domain
Natural inorganic gem materials
Browsing family
Oxide minerals
Identity tier
Mineral species
Mineral chemical class
Oxides / hydroxides
Construction or treatment status
Natural identity; treatment status unknown

Treatments listed by standards

Corundum is covered by GB/T 16552—2017, Annex B, Table B.1 through both the Ruby row and the Sapphire row. Under the Ruby row, heating is classed as optimization, dyeing as treatment, diffusion as treatment, and filling is graded. Under the Sapphire row, heating is classed as optimization, dyeing as treatment, diffusion as treatment, irradiation as treatment, and filling is likewise graded. The full Ruby and Sapphire rows of Table B.1, with the effect column, are on the Ruby and Sapphire pages respectively; what Table B.1 is and how the filling grades are defined are explained on the Gem treatments page.

GB/T 16552-2017, Annex B, Table B.1

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 nomenclature status of Corundum is IMA status G: grandfathered, meaning discovered before the IMA was founded and generally regarded as a valid mineral species; the composition (phase) is registered as corundum. Optically, the registered optical effect for corundum is the colour-change effect. On durability, filling of corundum has the status treated, with stability marked unstable; this site notes that the stability of filling refers to whether this treatment is stable, not to whether corundum itself is durable.

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”.

Definition

Corundum — nomenclature status: IMA status G: grandfathered (described before the IMA existed, and generally regarded as a valid species).

CIBJO Gemmological Laboratories Book 2024

Source & check 2026-09-22
Source
Fact checked on
2026-09-22

Corundum — composition (phase): corundum

CIBJO Gemmological Laboratories Book 2024

Source & check 2026-09-22
Source
Fact checked on
2026-09-22

Durability

Corundum — Mohs hardness: 9

GIA Gem Encyclopedia (care guide)

123456789109References (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)

Mohs hardnessSource: GIA Gem Encyclopedia (care guide)
Qualification

The source we cite gives a Mohs hardness but no figure for toughness or stability.

General note
hardness only, not durability
Source & check 2026-10-08
Source
Fact checked on
2026-10-08

For Corundum, the stability of filling is “unstable”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
filling
Qualification

This says how well the treatment holds up, not how durable Corundum itself is.

General note
no durability verdict here
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

Optical

Optical effects on record: colour change

Corundum — optical effect (colour change): colour-change.

CIBJO Gemmological Laboratories Book 2024

Source & check 2026-09-22
Source
Fact checked on
2026-09-22
CIBJO definitions
colour change

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

Testing and market

How far testing can go

Corundum — synthetic counterpart on the market: A synthetic counterpart of this material is commercially available

CIBJO Gemstone Book 2022

Treatment state
any treatment state
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

For Corundum in trade, the reported frequency of filling is “commonly”.

CIBJO Gemstone Book 2022

Treatment state
treated
Treatment
filling
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

Corundum is listed directly in CIBJO Gemmological Laboratories Book 2024 under the entry name Corundum, defined as mineral species corundum with IMA status G, with the CIBJO wording quoted in full under Clause-level definitions on this page; the cross-check result is that it is defined directly by CIBJO and also appears in the GB/T annex. Corundum also has an IMA Mineral List entry, registered as Corundum Al2O3 G 1714 and cross-checked against the RRUFF/IMA master mineral list; this is public domain data.

This table scrolls sideways on narrow screens.

TermClauseDefinitionCross-check
Corundum7.2.1.67see gem varieties colour-change sapphire, green sapphire, orange sapphire, Padparadscha, pink sapphire, purple sapphire, ruby, star ruby, sapphire, star sapphire, white sapphire, yellow sapphireDefined directly by CIBJO; also present in the GB/T annex.
CorundumIMA Mineral List entryCorundum Al2O3 G 1714Cross-checked against the RRUFF/IMA master mineral list (public domain data).

Evidence and sources

Authority basis and clause sources

GB/T 16552—2017
Listed Table A.1 “Corundum” · Source
IMA Mineral List 2026-07
Listed “Corundum” · Source
CIBJO Gemmological Laboratories Book 2024
Listed §7.2.1.67 “Corundum” · Source

Sources

Further reading

Related pages

Treatments recorded for this 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 Corundum on this site: 18 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Corundum) is marked.

This table scrolls sideways on narrow screens.

PageContentStatus
Browsing familyOxide mineralsLive
Treatments recorded for this materialHeated / Heat-treated, Dyed (via parent material), Filled / Fracture-filled (via parent material), Diffusion-treated (via parent material), Irradiated (via parent material)Live
Related articlesTo be added (placeholder)Planned

Who maintains this page

The material facts in the Corundum 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
Ralph
Reviewer
June
How facts are checked
Each fact is matched to the clause it cites; facts checked between 2026-09-22 and 2026-10-08
Last revised
2026-10-12
Purpose
Lets buyers and sellers check naming, disclosure and material facts clause by clause.

Spotted an error? Report it on the forum