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

Talc

Also known asSoapstone (conditional name) · Steatite

A mineral species listed in GB/T 16552-2017 Annex A.2. Talc has extremely low hardness, and Soapstone is not necessarily pure talc. Also known as Steatite. 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

Care and wear

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

Talc has the formula Mg3Si4O10(OH)2 and is one of the softest sheet-silicate minerals (Mohs hardness 1). It occurs in talc-rich schists or steatite, formed by hydrothermal alteration of mafic rocks (steatitization) that follows serpentinization during greenschist-facies metamorphism; talc can also form by low-temperature thermal metamorphism of siliceous dolostones. Its formation reflects reaction of magnesium-rich rocks with silica-bearing fluids under low-temperature metamorphic-hydrothermal conditions.

Scope: Applies to the genesis, composition, occurrence and appearance of talc as a natural magnesian layer silicate mineral species; does not cover synthetic materials.

Sources Handbook of Mineralogy

Where it forms

Talc-rich schists or steatite

Sources Handbook of Mineralogy

Hydrothermal alteration of mafic rocks after serpentinization, during greenschist-facies metamorphism

Sources Handbook of Mineralogy

Metamorphism of siliceous dolostone driven by low heat

Sources Handbook of Mineralogy

How it forms, step by step

  1. Mafic rocks first undergo serpentinization.

    Sources Handbook of Mineralogy

  2. During greenschist-facies metamorphism, silica-bearing hydrothermal fluids alter the magnesium rocks (steatitization).

    Sources Handbook of Mineralogy

  3. Talc-rich schists or steatite crystallize.

    Sources Handbook of Mineralogy

  4. Talc may alternatively form by low-temperature thermal metamorphism of siliceous dolostones.

    Sources Handbook of Mineralogy

Link to appearance

Talc is light to dark green, brown or white (colorless in thin section), with a white streak and a pearly, greasy or dull luster; with Mohs hardness 1 it feels greasy, and its cleavage flakes are flexible but not elastic.

Sources Handbook of Mineralogy

Timescale

The source states no absolute geological timescale for talc formation.

Sources Handbook of Mineralogy

Supporting findings

Talc occurs in talc-rich schists or steatite, formed by hydrothermal alteration of mafic rocks (steatitization) that follows serpentinization during greenschist-facies metamorphism.

Evidence grade B

Scope: Describes talc's natural hydrothermal-metamorphic origin; not laboratory synthesis.

Sources Handbook of Mineralogy

Talc can also form by low-temperature thermal metamorphism of siliceous dolostones.

Evidence grade B

Scope: Describes one metamorphic mode of talc formation; it is not the only origin.

Sources Handbook of Mineralogy

Talc typically occurs together with these minerals: calcite, dolomite, anthophyllite, serpentine, vermiculite, pyroxene, chlorite, tremolite and actinolite.

Evidence grade B

Scope: Describes talc's typical associations; not all localities share them.

Sources Handbook of Mineralogy

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).

Asia

  • Onot deposit, Irkutsk, RussiaMineral specimen locality (not a source of jewellery material)printed as Onotosk
    Sources Handbook of Mineralogy

Europe

  • Mt. Greiner, Zillertal, Tyrol, AustriaMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • Zermatt, Valais, SwitzerlandMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • St. Gotthard, Ticino, SwitzerlandMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • Trimouns talc deposit, near Luzenac, Ariège, FranceMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • Göpfersgrün, Bavaria, GermanyMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • Snarum, NorwayMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy

North America

  • Near Fowler, New York, United StatesMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • Delta, Pennsylvania, United StatesMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • Rochester, Vermont, United StatesMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • Holly Springs, Georgia, United StatesMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy
  • Near San Andreas, Calaveras County, California, United StatesMineral specimen locality (not a source of jewellery material)
    Sources Handbook of Mineralogy

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.

Where the name comes from

The English name talc probably derives from the Arabic talq.

Evidence grade B

Scope: Etymology explains the origin of the name only; it does not establish the material's composition, locality, naturalness, or treatment.

Sources Handbook of Mineralogy

Human use and museum objects

Objects held by The Met from Egypt (Middle–New Kingdom), Minoan Crete and Central Anatolia — beads, a vase, a cauldron and a stamp seal — are labelled 'steatite' (compact massive talc) in the museum's medium field, ranging from an Egyptian Old Kingdom cowroid bead (10.130.2950, ca. 2649 BCE) to an Iranian steatite cauldron of the 9th century (38.40.161); steatite was thus used as a bead and vessel material from at least the third millennium BCE.

Evidence grade A

Scope: Based only on the museum's cataloguing of these specific objects; it is not generalized to widespread practice or universal use of the material.

Sources The Met 10.130.2950 · The Met 30.8.323 · The Met 30.8.629 +5

The medium fields must be read as the museum wrote them: The Met records these objects as 'steatite', and 'steatite' (compact massive talc) and 'serpentine' (snake-stone) are different minerals that should not be conflated; this entry does not equate steatite with serpentine.

Evidence grade A

Scope: Based only on the museum's cataloguing of these specific objects; it is not generalized to widespread practice or universal use of the material.

Sources The Met 10.130.2950 · The Met 30.8.323 · The Met 30.8.629 +5

The museum-material word for these objects is 'steatite' (compact massive talc), not 'talc' powder nor 'serpentine' (snake-stone); the three are not interchangeable. The Met holds Egyptian glazed-steatite beads, bead plaques and cowroid beads of the Middle–New Kingdom (e.g. 10.130.2950 'Cowroid Bead', ca. 2649–1640 BCE; 30.8.323 'Bead, Yakobher', ca. 2030–1640 BCE; 30.8.629 'Bead Plaque', ca. 1300–1200 BCE; 26.7.231 'Bead plaque', ca. 1290–1224 BCE), which are among the earlier attested steatite ornaments. The same museum holds a Minoan steatite vase with a spout (26.31.429, ca. 2600–1900 BCE), an Iranian steatite cauldron (38.40.161, 9th century) and an Old Assyrian black-steatite stamp seal (99.22.3, ca. 18th century BCE, Central Anatolia); the Cleveland Museum of Art holds an Egyptian New Kingdom necklace fragment (1915.15, 1540–1296 BCE) whose medium includes steatite. Steatite as a bead and vessel material is thus attested from at least the third millennium BCE in Egypt and Minoan Crete through to the first millennium CE.

Sources The Met 10.130.2950 · The Met 30.8.323 · The Met 30.8.629 +5

Scope: A museum object evidences only that artefact's existence and date; it does not establish widespread ancient use of the material, nor does it authenticate the origin, naturalness or treatment of any modern specimen.

Objects cited

3000 BCE2000 BCE1000 BCE01000Met 10.130.2950ca. 2649–1640 BCEMet 26.31.429ca. 2600–1900 BCEMet 30.8.323ca. 2030–1640 B.C.Met 99.22.3ca. 18th century BCECMA 1915.151540–1296 BCEMet 30.8.629ca. 1300–1200 BCEMet 26.7.231ca. 1290–1224 BCEMet 38.40.1619th century
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 10.130.2950Cowroid Bead · ca. 2649–1640 BCE · EgyptSteatite
  • The Met 30.8.323Bead, Yakobher · ca. 2030–1640 B.C. · EgyptSteatite
  • The Met 30.8.629Bead Plaque · ca. 1300–1200 BCE · EgyptSteatite
  • The Met 26.7.231Bead plaque · ca. 1290–1224 BCE · EgyptSteatite
  • The Met 26.31.429Steatite vase with spout and lugs · ca. 2600–1900 BCE · MinoanSteatite
  • The Met 38.40.161Cauldron · 9th century · IranSteatite; carved
  • The Met 99.22.3Stamp seal with a knob handle: bird of prey with two horned animals caught in its talons · ca. 18th century BCE · Old Assyrian Trading Colony · Central AnatoliaBlack steatite
  • Cleveland Museum of Art 1915.15Fragment of a Necklace · 1540–1296 BCE · Egypt, New Kingdom (1540–1069 BCE), Dynasty 18steatite, glass, carnelian, and faience

Other research findings

Talc has the formula Mg3Si4O10(OH)2 and a Mohs hardness of 1, making it a very soft sheet-silicate mineral.

Evidence grade B

Scope: Describes talc's composition and hardness; not industrial purity grading.

Sources Handbook of Mineralogy

Limits of this research

  • Research status: Formation, occurrence or other material-specific findings found in authoritative sources
  • The source states no absolute geological timescale for talc formation.
  • The source does not quantify the specific temperature and fluid conditions of steatitization.

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
Talc

GB/T 16552—2017 Table A.2 “Talc” · IMA Mineral List 2026-07 “Talc”

Construction or treatment status

Natural identity; treatment status unknown

Treatments recorded for this material: Dyed, Coated

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

Talc is also known by several other names, some of which can refer to different materials in other contexts; use "Talc" to avoid ambiguity.

Evidence

  • GB/T · Table A.2, row 滑石 (Talc)

What this means for you

Before buying, check the recommended listing name "Talc" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.

Known uncertainty

Last reviewed
2026-09-01

Care and wear

Normal care for every gemstone (CIBJO Gemstone Book §6.1), in brief:

  • Handle it gently.
  • Store pieces apart when not worn, so they cannot scratch each other.
  • Clean with warm soapy water and a soft brush.
  • Use ultrasonic cleaners only with caution.

The §6.1 wording and the full list of §6.2 special-care letters cited on this page are on the general gem care page.

Care

Talc — care (cleaning): Some stones are susceptible to damage from ultrasonic cleaning. Do not expose them to ultrasonic cleaning.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code j

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

Talc — care (chemicals): Treatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code k

Treatment state
treated
Only after these treatments
dyeing
Source & check 2026-09-25
Source
Fact checked on
2026-09-25

Talc — care (chemicals): Some stones are porous. Do not allow contact with coloured fluids.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code c

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

Talc — care (wear): low hardness, so it scratches easily; wear with care; cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care.

CIBJO Gemstone Book 2022

CIBJO Gemstone Book §6.2:special-care code a, special-care code b

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

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

Common care questions and matching entries

WearThe care and wear conclusions registered for Talc from the CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) are as follows. Cleaning: it must not be cleaned ultrasonically, for any treatment state. Chemicals: for dyed Talc, with the treatment state treated and limited to dyeing, treatments with dye, oil, resin, wax or plastic are not permanent, so keep it away from all solvents (including dish-washing liquids), chemicals and heat; the chemicals conclusion for any treatment state states that Talc is porous and should not come into contact with coloured fluids. Wear: the conclusions for any treatment state state that Talc has low hardness and scratches easily, so wear it with care, and that it breaks easily, so wear it with care.

This table scrolls sideways on narrow screens.

QuestionMatching entries
Can it go in an ultrasonic or steam cleaner?care (cleaning)
Contact with acids, alkalis and household chemicalsTreatments with dye, oil, resin, wax or plastic are not permanent; keep it away from all solvents (including dish-washing liquids), chemicals and heat; care (chemicals)
Wearing limits (knocks, settings)low hardness, so it scratches easily; wear with care; cleaves or fractures easily or is brittle (e.g. rubbed facet edges); wear with care

Care entries by treatment state

The same entries grouped by the treatment state each applies to; each links to its full wording and source. Letters are CIBJO special-care codes, explained on the gemstone care page.

any treatment state

treated (Only after these treatments: dyeing)

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.

TreatmentMarket frequency (CIBJO)Stability (CIBJO)GB/T 16552 categoryJJA/AGL listingIdentification leads
coatingStatus: treated——Treatment—See identification leads
dyeingStatus: colour treated——Treatment—See identification leads

Where each treatment acts (schematics): Coated · Dyed

“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16553—2017; GB/T 16552—2017 Table B.1

Whether a treatment has to show in the name differs between the two rule sets (this site’s paraphrase):

  • GB/T 16552—2017: a method classed as treatment has to be stated in the name itself — the method put before the name, or added in brackets after it; a method classed as optimization does not need to appear in the name, though one marked “Optimization (annotation required)” still has to be noted in the quality documents. Source: §5.4.2.1 a), b); §5.4.2.2 a)
  • CIBJO Gemstone Book 2022: no longer splits treatments into ones that need specific disclosure and ones that need only general disclosure: every treatment is to be disclosed, and the seller tells the buyer which treatment was used and what special care it calls for. Source: §4.2.5 Note 2, §4.2.5.1, pp.14–15

What this table covers

What this page can give

  • Registered treatments, their stability and how often they occur (see the table above)
  • Identification leads for each treatment, for use when sending a stone for testing

VerifyNames, standards, technical facts, clauses and sources

Names

Besides Talc, the name register records "Soapstone" and "Steatite", for which no restriction on use as a name is recorded (CIBJO Gemstone Book 2022 Annex 8 “Steatite”).

Chinese standard nameThe Chinese formal name of Talc is given in GB/T 16552—2017 Table A.2, and the mineralogical name is Talc. Names in four languagesThe four-language names are the Simplified and Traditional Chinese names, English Talc and the Japanese names, with the GSJ (Japan) formal name written in kanji. Recommended listing nameThe suggested listing name is Talc. Trade and mineralogical namesThe trade name or synonym is Soapstone (for rock or aggregate material), and Soapstone is not necessarily pure Talc; Steatite is a synonym recorded in Annex 8 of the CIBJO Gemstone Book 2022. Institution usageFor authority wording, CIBJO records “Talc” (CIBJO Gemmological Laboratories Book 2024), and GIA, FTC and Gem-A are unchecked; bodies without a recorded wording show the entry's own English name, which does not represent their position.

Name register

Every name recorded for this entry, with how it is classified, whether it may be matched to this entry automatically, whether it may be used as a product name, and the clause it rests on.

This table scrolls sideways on narrow screens.

NameTypeMatchingUse as a nameBasis
no restriction recorded (2)
SoapstoneEnglishmarket namematched only once the condition is confirmedno restriction recordededitorial ruling (no clause cited)
SteatiteEnglishsynonymmatched automaticallyno restriction recordedCIBJO Gemstone Book 2022 Annex 8 “Steatite”

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

Authority wording

GIA, FTC, CIBJO, Gem-A
Talc (on record for CIBJO (CIBJO Gemmological Laboratories Book 2024); GIA, FTC, Gem-A unchecked — bodies without a recorded wording show the entry's own English name)
GSJ (Japan) formal name
滑石
Chinese formal name
滑石 (GB/T 16552—2017 Table A.2)
Mineralogical name
Talc
Trade names and synonyms
Soapstone (market name; conditional name) · Steatite (synonym)

Four-language names

简体中文
滑石
繁體中文
滑石
English
Talc
日本語
タルク／滑石

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

Classification

Origin
Natural materials
Material domain
Natural inorganic gem materials
Browsing family
Other silicate minerals
Identity tier
Mineral species
Mineral chemical class
Silicates
Construction or treatment status
Natural identity; treatment status unknown

Treatments listed by standards

In GB/T 16552—2017 Annex B, Table B.1, the Talc row lists dyeing (effect: changes colour; category: treatment) and coating (effect: improves or changes lustre, colour and other aspects of appearance; category: treatment). What Table B.1 is and how each grade is defined are explained on the Gem treatments page.

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

Table B.1, row “Talc” (p.17):

This table scrolls sideways on narrow screens.

MethodEffectCategory
DyeingChanges colourTreatment
CoatingImproves or changes lustre, colour and other aspects of appearanceTreatment

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 composition (chemistry) of Talc is Mg3Si4O10(OH)2, and the phase is talc; the structure is a crystalline aggregate, usually compact and massive. Mohs hardness is registered as 1–3 under GB/T 16553—2017, while the Handbook of Mineralogy — Talc gives a Mohs hardness of 1; GB/T 16553—2017 registers no cleavage, while the Handbook of Mineralogy — Talc registers perfect cleavage for untreated talc, with a sectile tenacity, flexible but not elastic. Density is registered as 2.2–2.8 g/cm³, a range derived from the cited clause value of 2.75 with an allowed deviation of +0.05/−0.55; it feels greasy to the touch. Optically it is an anisotropic aggregate, and the refractive index is registered as 1.538–1.6, a range derived from the cited clause value of 1.540–1.590 with an allowed deviation of +0.010/−0.002; birefringence cannot be measured in aggregates, and transparency is translucent to opaque. Untreated talc has a waxy to greasy lustre.

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

Talc — 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

Talc — composition (chemistry): Mg3Si4O10 (OH) 2

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — composition (phase): talc

CIBJO Gemmological Laboratories Book 2024

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

Structure

Talc — structure (overall): crystalline aggregate, typically compact and massive

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Durability

Mohs hardness2 sources compared

12345678910GB/T 16553—20171–3Handbook of Mineralogy1References (diamond = value, bar = range; below)

Reference points on this site: Gypsum 1.5–2, Calcite 3, Quartz 7 (Source: Handbook of Mineralogy); Fluorite 4, Apatite 5–5.5, Orthoclase 6–6.5, Topaz 8, Diamond 10 (Source: GB/T 16553—2017); Corundum 9 (Source: GIA Gem Encyclopedia (care guide))

Mohs hardnessSource: GB/T 16553—2017 · Handbook of Mineralogy

Talc — Mohs hardness: 1–3

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Talc — Mohs hardness: 1

Handbook of Mineralogy

Source & check 2026-09-20
Source
Fact checked on
2026-09-20

Talc — cleavage: none

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — toughness: cleavage perfect; tenacity sectile, flexible but not elastic.

Handbook of Mineralogy

Treatment state
untreated
Source & check 2026-09-20
Source
Fact checked on
2026-09-20

Physical properties

Talc — density: 2.2–2.8 g/cm³

GB/T 16553—2017

0.51.52.53.54.55.56.57.52.2–2.8
Specific gravitySource: GB/T 16553—2017
Does this standard apply
applies to this entry
Qualification

The clause we cite gives 2.75, with a stated tolerance of +0.05 / -0.55. The range shown here is worked out from that.

Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — feel (texture): feels slippery to the touch

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Optical

Talc — optic character: anisotropic material

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — refractive index: 1.538–1.6

GB/T 16553—2017

1.31.72.12.52.93.31.538–1.6
Refractive indexSource: GB/T 16553—2017
Does this standard apply
applies to this entry
Qualification

The clause we cite gives 1.540–1.590, with a stated tolerance of +0.010 / -0.002. The range shown here is worked out from that.

Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — birefringence: not measurable on an aggregate

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — transparency: translucent to opaque.

CIBJO Gemmological Laboratories Book 2024

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

Talc — pleochroism: not measurable on an aggregate

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — fluorescence (overall): long wave none to weak, pink

GB/T 16553—2017

UV fluorescencepinknone–weakDots are illustrative colours built from the colour names, not measured values

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — spectrum (UV-visible): non-characteristic

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — spectrum (infrared): Talc's own diagnostic bands are seen in the mid-IR

GB/T 16553—2017

Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — magnification: structure ranging from cryptocrystalline to finely granular, compact massive structure, generally impurities appearing as veins and spots.

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

body colour2 sources compared

Talc — body colour: light to dark green, white, grey, brown, etc.

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Qualification

In chapter 5 of GB/T 16553—2017, the colour entries of Sillimanite, Vesuvianite / Idocrase, Brucite and other variety clauses also name green or a greenish colour.

General note
colour alone is not identity
Source & check 2026-09-26
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-26)
Fact checked on
2026-09-26

Talc — body colour: white, grey, brown, light to dark green, often mottled or veined.

CIBJO Gemmological Laboratories Book 2024

Treatment state
untreated
Qualification

In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Sillimanite, Tremolite, Magnesite and other entries also name white or a whitish colour.

General note
colour alone is not identity
Source & check 2026-09-22
Source
Fact checked on
2026-09-22

How the sources relate

GB/T 16553—2017 and CIBJO Gemmological Laboratories Book 2024

consistent

The two entries agree: light to dark green, white, grey and brown. The CIBJO Gemmological Laboratories Book gives this under soapstone, with talc as the mineral species, and notes that it is often mottled or veined.

Quality factors

Talc — quality factor (lustre): waxy and greasy

GB/T 16553—2017

Treatment state
untreated
Does this standard apply
applies to this entry
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (locator checked 2026-09-21)
Fact checked on
2026-09-21

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

1.551.561.571.581.591.62.42.52.62.72.8Refractive indexSpecific gravity12345Talc

This material (RI / SG midpoints): 1.569 / 2.5; Closest values: 1Changhua Stone 1.56 / 2.6, 2Howlite 1.595 / 2.52, 3Bamboo Coral 1.57 / 2.65, 4Charoite 1.554 / 2.66, 5Synthetic Beryl 1.57 / 2.69

Show the full chart (330 registered materials)1.41.51.61.71.81.922.12.22.32.41234567Refractive indexSpecific gravity12345Talc

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

How far testing can go

Talc that has undergone coating can be identified by the following features: Under magnification the surface luster is abnormal and the film can be seen peeling off in places; refractive index readings may be abnormal; infrared and Raman spectra show characteristic peaks of the film.

GB/T 16553—2017

Treatment state
treated
Does this standard apply
can be followed as a reference only
Treatment
coating
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (coating) (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc that has undergone dyeing can be identified by the following features: Under magnification the colour is unevenly distributed and mostly concentrated in fissures, between grains or in surface hollows; wiping with acetone or absolute ethanol can lift the colour.

GB/T 16553—2017

Treatment state
colour treated
Does this standard apply
can be followed as a reference only
Treatment
dyeing
Source & check 2026-09-21
Source
  • GB/T 16553—2017 Gems — Testing (GB/T): §5.2.24 (dyeing) (locator checked 2026-09-21)
Fact checked on
2026-09-21

Talc — 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

Talc is defined directly in the Talc entry of CIBJO Gemmological Laboratories Book 2024, as mineral species talc 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. The visible definition in the Soapstone entry of CIBJO Gemmological Laboratories Book 2024 describes a translucent to opaque material, often mottled or veined, in white, grey, brown or light to dark green; the cross-check is that it is defined directly by CIBJO and no identically named English entry was found in the GB/T annex, and Soapstone is not necessarily the same as pure talc. The Talc entry in the IMA Mineral List gives the chemical formula Mg3Si4O10(OH)2 and IMA status G with a question mark; it is cross-checked against the RRUFF/IMA master mineral list, and the source is marked as public domain data.

This table scrolls sideways on narrow screens.

TermClauseDefinitionCross-check
Soapstone7.2.1.220white, grey, brown, light to dark green, often mottled or veined; translucent to opaqueDefined directly by CIBJO; no identically named English entry was found in this edition of the GB/T annex.
Talc7.2.1.234white, grey, brown, light to dark green, often mottled or veined; translucent to opaque. See also soapstoneDefined directly by CIBJO; also present in the GB/T annex.
TalcIMA Mineral List entryTalc Mg3Si4O10(OH)2 G ?Cross-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.2 “Talc” · Source
IMA Mineral List 2026-07
Listed “Talc” · Source
CIBJO Gemmological Laboratories Book 2024
Listed §7.2.1.234 “Talc” · 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.

This table scrolls sideways on narrow screens.

PageContentStatus
Browsing familyOther silicate mineralsLive
Treatments recorded for this materialDyed, CoatedLive
Related articlesTo be added (placeholder)Planned

Who maintains this page

The material facts in the Talc 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 2026-09-26
Last revised
2026-10-12
Purpose
Lets buyers and sellers check naming, disclosure and material facts clause by clause.

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