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Natural inorganic gem materials · Mineral species · Natural identity; treatment status unknown
Brucite
A magnesium hydroxide mineral species with the formula Mg(OH)2, listed in GB/T 16552—2017 Table A.2 as "Brucite"; its hardness is rather low. This page compares how the major standards and institutions name it, what must be disclosed when selling it, whether it can be worn every day, how it is treated and identified, and which source each conclusion comes from.
Price, rarity and origin are outside the scope of this wiki.
What this page can answer
This page covers
- How Brucite forms and what gives its colourFormation setting, process and timescale; where its colour and optical effects come from, each finding graded and sourced
- Caring for and wearing BruciteCleaning, heat, chemicals and light, as the cited sources give them; durability indicators and wearing advice
- Hardness, density and refractive index of BruciteEach value with its source and check date
- Brucite in English, Chinese and Japanese; national standard namesNames in four languages, the GB/T standard name and the suggested listing name; and: Has any of GIA, FTC, CIBJO or Gem-A put a name for it on record here?
- Name origin and history of BruciteWhere the name comes from
- Listing and disclosing BruciteThe listing name to use; what must be disclosed before sale
- Standard clauses that define BruciteWhich clause defines it, each cross-checked
What we cannot conclude
- Whether one particular bead is natural, treated or synthetic — only a laboratory report can settle that.
- Geographic origin, unless an origin report accompanies the item.
- Price, rarity or investment value: this wiki covers naming and disclosure only.
Material research: formation, causes and history
What authoritative sources say about how this material forms, what causes its colour and optical effects, where its name comes from and how people have used it. Each statement carries an evidence grade and its sources; it describes the material in general, not any specific piece.
How it forms
A hydroxide mineral of the brucite group, brucite has the composition Mg(OH)2. It most often appears as an alteration product of periclase within marble, though it also forms veins of low-temperature hydrothermal origin in chlorite schists and metamorphic limestones, and it is produced when dunites are serpentinized. Crystals are typically tabular and gathered into platy, fibrous or massive aggregates; hardness is low and cleavage perfect. Colour is usually white, pale green, blue or gray, while manganoan varieties run to honey-yellow, brownish red and deep brown.
Scope: Applies to the genesis, occurrence and composition of natural brucite as a mineral species; does not cover industrial magnesium hydroxide products or flame-retardant applications.
Sources Handbook of Mineralogy
Where it forms
Periclase within marble, commonly altered to brucite
Sources Handbook of Mineralogy
Vein mineral of low-temperature hydrothermal origin hosted by chlorite schists and metamorphic limestones
Sources Handbook of Mineralogy
Formed during the serpentinization of dunites and other ultramafic rocks
Sources Handbook of Mineralogy
How it forms, step by step
In dolomitic marble, periclase is altered by hydration to form brucite.
Sources Handbook of Mineralogy
In metamorphic limestones and chlorite schists, low-temperature hydrothermal fluids precipitate brucite in veins.
Sources Handbook of Mineralogy
During serpentinization of ultramafic rocks, magnesian fluids react to form brucite, associated with serpentine minerals.
Sources Handbook of Mineralogy
Link to appearance
Brucite has low hardness (about 2.5), perfect cleavage, and waxy to pearly luster; it is mostly white, pale green, blue, or gray, with manganoan varieties honey-yellow to deep brown. Its platy, fibrous, or massive habit relates directly to its low hardness and easily separable cleavage plates.
Sources Handbook of Mineralogy
Timescale
The source states no absolute geological timescale for brucite formation.
Sources Handbook of Mineralogy
Supporting findings
In marble, brucite is a widespread alteration product of periclase; it occurs as a vein mineral of low-temperature hydrothermal origin in chlorite schists and metamorphic limestones, and it is also generated when dunites undergo serpentinization.
Evidence grade BScope: Describes brucite's several natural formation pathways.
Sources Handbook of Mineralogy
Brucite commonly occurs with chrysotile, talc, artinite, hydromagnesite, magnesite, dolomite, aragonite and calcite.
Evidence grade BScope: Describes brucite's associations and occurrence context.
Sources Handbook of Mineralogy
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Africa
- Ethyl mine, Mutorashanga, Zimbabwe
Sources Handbook of Mineralogy
- Phalaborwa, South Africa
Sources Handbook of Mineralogy
Europe
- Mt. Vesuvius, Campania, Italy
Sources Handbook of Mineralogy
- Teulada, Sardinia, Italy
Sources Handbook of Mineralogy
- Unst, Shetland Islands, Scotland, United Kingdom
Sources Handbook of Mineralogy
- Asbest, Ural Mountains, Russia
Sources Handbook of Mineralogy
North America
- Castle Point, Hoboken, New Jersey, United States
Sources Mindat: Brucite · Handbook of Mineralogy
- Wood's Chrome mine, near Texas, Lancaster County, Pennsylvania, United States
Sources Handbook of Mineralogy
- Tilly Foster mine, Brewster, New York, United States
Sources Handbook of Mineralogy
- Near Gabbs, Nye County, Nevada, United StatesHoM: a large deposit
Sources Handbook of Mineralogy
- Crestmore quarry, Riverside County, California, United States
Sources Handbook of Mineralogy
- Val-des-Sources (Asbestos), Quebec, Canadaprinted as Asbestos
Sources Handbook of Mineralogy
- Wakefield, Quebec, Canada
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 the origin determination guide and the overview of recorded localities.
Causes of colour and optical effects
Brucite is typically white, pale green, blue, or gray, while manganoan varieties range from honey-yellow to deep brown and brownish red; the color is controlled by composition, particularly manganese content.
Evidence grade BScope: Describes the compositional (especially manganese) basis of brucite's color.
Sources Handbook of Mineralogy
Where the name comes from
Brucite commemorates Archibald Bruce (1777–1818), an early American physician and mineralogist who taught at New York's College of Physicians and Surgeons, later Columbia University, and was the first to describe the species.
Evidence grade BScope: The etymology explains the origin of a name only; it does not attest composition, locality, naturalness or treatment.
Sources Handbook of Mineralogy
Other research findings
Brucite has the formula Mg(OH)2, belongs to the brucite group, and its composition can be expressed as (Mg,Fe)(OH)2.
Evidence grade BScope: Concerns brucite's composition and group.
Sources Handbook of Mineralogy
The name brucite honours Archibald Bruce (1777-1818), an early American mineralogist who was also a physician.
Evidence grade BScope: Concerns the name's origin, not genesis.
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 age or P-T conditions for brucite formation.
Methodology
- Origin determination and its limits
- Quality grading and value factors
- How gemmology became a technical discipline
Evidence grades
- A
- Standards bodies, government geological surveys, peer-reviewed research and museum records
- B
- Institutional educational material
- C
- Specialist databases or cautious readings
A statement is never graded above its strongest source.
This section is LumaLark's own factual restatement of public authoritative sources, credited item by item; it contains no verbatim excerpts, images or third-party logos.
DecideListing name, disclosure, care and treatments
- Suggested listing name
- Brucite
GB/T 16552—2017 Table A.2 “Brucite” · IMA Mineral List 2026-07 “Brucite”
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
Brucite is Brucite (Mg(OH)2); use "Brucite" for listings, and disclose any known treatments.
Evidence
- GB/T · Table A.2, row 水镁石 (Brucite)
What this means for you
Before buying, check the recommended listing name "Brucite" 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
Brucite — care (chemicals): the Oxford Mineral Susceptibility Database notes that brucite dissolves readily in acids
Mineral Sensitivity Database, Oxford (2021)
- Treatment state
- any treatment state
Source & check 2026-10-06
- Source
- K. Royce, “The Mineral Susceptibility Database” (MSD-2021.06), University of Oxford (2021), doi:10.5287/bodleian:r17kVJb7d: Section: main text (locator checked 2026-10-06)
- 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.
| Question | Matching entries |
|---|---|
| Contact with acids, alkalis and household chemicals | the Oxford Mineral Susceptibility Database notes that brucite dissolves readily in acids |
Durability and wearing
Numbers in curly braces, such as {111}, are crystallographic face symbols (Miller indices): each marks a set of crystal faces or cleavage planes. They are reproduced as written in the cited source.
Toughness
Sectile; plates flexible, fibers elastic
VerifyNames, standards, technical facts, clauses and sources
Names
Standard and listing namesThe Chinese formal name for Brucite comes from GB/T 16552—2017 Table A.2, and the suggested listing name is Brucite. Trade and mineralogical namesThe mineralogical name is Brucite (Mg(OH)2). Names in four languagesThe four-language names cover Simplified Chinese, Traditional Chinese, English (Brucite) and Japanese; the GSJ (Japan) formal name is a separate Japanese form. Institution usageOn authority wording, the FTC and CIBJO texts have no wording for the name Brucite (checked), and the wording of GIA and Gem-A is unchecked. Bodies without a record show the material's own English name, Brucite, which does not represent their position.
- GSJ (Japan) formal name
- 水滑石（ブルース石）
- Chinese formal name
- 水镁石 (GB/T 16552—2017 Table A.2)
- Mineralogical name
- Brucite (Mg(OH)2)
Four-language names
- 简体中文
- 水镁石
- 繁體中文
- 水鎂石
- English
- Brucite
- 日本語
- ブルーサイト／水滑石
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
What it is and how it's identified
Brucite is registered under GB/T 16553—2017: composition Mg(OH)2; the structure is a crystalline aggregate, usually of flakes, plates or grains; Mohs hardness 2–3, density 2.38–3.4 g/cm³. The optical character is an anisotropic aggregate, and birefringence is not measurable for an aggregate. Refractive index 1.57; the site qualifies this as the reading commonly obtained by the spot method, a typical value rather than an absolute limit. The UV-visible spectrum is not diagnostic, and the mid-infrared region shows the characteristic infrared absorption bands of brucite. Untreated Brucite has a vitreous lustre, pearly on cleavage surfaces.
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
Brucite — composition (chemistry): Mg(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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Structure
Brucite — structure (overall): crystalline aggregate, usually made of flakes, plates or grains.
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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Durability
Brucite — Mohs hardness: 2–3
GB/T 16553—2017
Reference points on this site: Talc 1–3, Fluorite 4, Apatite 5–5.5, Orthoclase 6–6.5, Topaz 8, Diamond 10 (Source: GB/T 16553—2017); Gypsum 1.5–2, Calcite 3, Quartz 7 (Source: Handbook of Mineralogy); Corundum 9 (Source: GIA Gem Encyclopedia (care guide))
- Does this standard apply
- applies to this entry
- General note
- hardness only, not durability
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Physical properties
Brucite — density: 2.38–3.4 g/cm³
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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Brucite — optic character: anisotropic 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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Brucite — refractive index: 1.57
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives this as a value commonly read by the spot (distant-vision) method. It is a common value, not an absolute limit.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Brucite — 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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Brucite — 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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Brucite — fluorescence (overall): none
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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Brucite — 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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Brucite — spectrum (infrared): diagnostic bands of brucite 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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Brucite — magnification: platy or granular structure
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): §5.2.35 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Brucite — body colour: white, grey, light green, yellow, brownish red, 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 Mica Jade, Amber, Quartzite Jade and other variety clauses also name white or a whitish colour.
- General note
- colour alone is not identity
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.35 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Quality factors
Brucite — quality factor (lustre): vitreous; cleavage surfaces show a pearly lustre.
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): §5.2.35 (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.
This material (RI / SG midpoints): 1.57 / 2.89; Closest values: 1Muscovite 1.58 / 2.8, 2Qingtian Stone 1.565 / 2.77, 3Lepidolite 1.55 / 2.8, 4Natural Conch Pearl / Natural Melo Pearl 1.595 / 2.84, 5Calcite 1.572 / 2.7
Show the full chart (330 registered materials)
Outside the full chart's range, drawn as triangles at the edge (RI / SG midpoints): Hematite 3.045/5.12, Synthetic Rutile 2.76/4.26, Rutile 2.753/4.23, Synthetic Moissanite 2.67/3.22
Clause-level definitions
In the clause-level definitions, Brucite is recorded under the English term Brucite. The definition given in GB/T 16552—2017 Annex A reads Brucite (Mg(OH)2); the cross-check result is listed directly by GB/T, with no standalone CIBJO entry under the same name. The IMA mineral list entry gives the definition as Brucite Mg(OH)2 G 1818, cross-checked against the RRUFF/IMA mineral list master table, using public-domain data.
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Brucite | GB/T 16552-2017 Annex A | Brucite (Mg(OH)2) | Listed directly by GB/T; CIBJO carries no standalone entry under the same name. |
| Brucite | IMA Mineral List entry | Brucite Mg(OH)2 G 1818 | Cross-checked against the RRUFF/IMA master mineral list (public domain data). |
Evidence and sources
Authority basis and clause sources
Sources
- CIBJO – The World Jewellery Confederation. Gemmological Laboratories Book (Blue Book), Gemmological Commission 2024-1.
- CIBJO – The World Jewellery Confederation. The Gemstone Book (Blue Book), 2022.
- SAMR / SAC (China). GB/T 16552—2017 Gems — Nomenclature.
- RRUFF Project, in partnership with the IMA – International Mineralogical Association. IMA Mineral List.
- Geological Survey of Japan, AIST (Japan). Museum mineral specimens, browse by classification.
Further reading
Related entries and topic cluster
Parent entry and related pages on this site. Rows marked “Planned” are suggested new content and have no link yet.
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Oxide minerals | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Brucite 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.