On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Mineral species · Natural identity; treatment status unknown
Sillimanite
Also known asFibrolite · Sillimanite Cat's-eye
A silicate mineral species listed in GB/T 16552-2017 Appendix A.1; its fibrous material keeps the traditional name Fibrolite. 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 Sillimanite forms and what gives its colourFormation setting, process and timescale, each finding graded and sourced
- How to identify SillimaniteHow far lab testing can go and whether a synthetic exists
- Caring for and wearing SillimaniteCleaning, heat, chemicals and light, as the cited sources give them; durability indicators and wearing advice
- Hardness, density and refractive index of SillimaniteEach value with its source and check date
- Sillimanite in English, Chinese and Japanese; national standard namesNames in four languages, the GB/T standard name and the suggested listing name; and: Which of GIA, FTC, CIBJO and Gem-A have a name for it on record, and do those agree?
- Name origin and history of SillimaniteWhere the name comes from
- Listing and disclosing SillimaniteThe listing name to use; what must be disclosed before sale
- Standard clauses that define SillimaniteWhich 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
Sillimanite, Al2SiO5, is an aluminium nesosilicate. High-grade metamorphic schists, gneisses and hornfels host it, it is more rarely found in pegmatites, and it can also occur as a detrital grain. The essential relationship is trimorphism: sillimanite, kyanite and andalusite share one composition but adopt different crystal structures. Within the Al2SiO5 system, sillimanite is the stable phase under high-grade (high-temperature) metamorphism, kyanite under high pressure, and andalusite under conditions of low pressure and low temperature; note, though, that the present source (HoM) confirms only the trimorphous relationship and provides no specific P-T stability fields.
Scope: Applies to the genesis, polymorphic relationships and occurrence of sillimanite as a natural Al2SiO5 mineral species; does not cover gem variety nomenclature or synthetic materials.
Sources Handbook of Mineralogy
Where it forms
Hornfels, gneisses and schists of high metamorphic grade
Sources Handbook of Mineralogy
Pegmatites, but rarely
Sources Handbook of Mineralogy
Detrital sedimentary settings (as a detrital mineral)
Sources Handbook of Mineralogy
How it forms, step by step
Aluminium-rich protoliths undergo high-grade (high-temperature) metamorphism.
Sources Handbook of Mineralogy
Sillimanite crystallizes in high-grade schists, gneisses and hornfels, often as fibrous mats (fibrolite).
Sources Handbook of Mineralogy
In the Al2SiO5 system, sillimanite is trimorphous with kyanite and andalusite under different P-T conditions.
Sources Handbook of Mineralogy
Sillimanite may also crystallize in pegmatites, or survive weathering and transport as a detrital mineral.
Sources Handbook of Mineralogy
Link to appearance
Sillimanite may be colorless or white to gray, also brown, yellow, yellow-green, gray-green, blue-green to blue, with a white streak and vitreous to subadamantine luster; crystals are prismatic, may be acicular with square cross sections, or form fibrous mats.
Sources Handbook of Mineralogy
Timescale
The source states no absolute geological timescale for sillimanite formation; its stability is defined by P-T conditions, not absolute age.
Sources Handbook of Mineralogy
Supporting findings
Sillimanite occurs in high-grade metamorphic schists, gneisses and hornfels, and more rarely in pegmatites.
Evidence grade BScope: Describes sillimanite's metamorphic and pegmatite occurrence; not other settings.
Sources Handbook of Mineralogy
In the Al2SiO5 polymorph series, sillimanite is stable under high-temperature (low- to medium-pressure) metamorphism, kyanite under high pressure, and andalusite under low pressure and low temperature (standard mineralogical understanding; the present source only confirms the trimorphous relationship).
Evidence grade BScope: The P-T fields are standard mineralogy, not quantified in the cited source, so they are not carried by a verbatim quote.
Sources Handbook of Mineralogy
Sillimanite is commonly associated with andalusite, kyanite, potassic feldspar, almandine, cordierite, biotite and quartz.
Evidence grade BScope: Describes sillimanite'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.
Asia
- Okkampitiya, Ratnapura, Deniyaya and Balangoda districts, Sri LankaListed as a source of gem crystals
Sources Handbook of Mineralogy
- Carnatic coast, Tamil Nadu, IndiaOne of the co-type localities
Sources Mindat: Sillimanite
North America
- Chester, Middlesex County, Connecticut, United StatesOne of the co-type localities
Sources Mindat: Sillimanite · Handbook of Mineralogy
Seas and coasts
- WorldwideWidespread, but fine examples are uncommon
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 sillimanite commemorates Benjamin Silliman (1779–1864), who taught chemistry and mineralogy as a professor at Yale University in New Haven, Connecticut, USA.
Evidence grade BScope: Etymology explains the origin of the name only; it does not establish the material's composition, locality, naturalness, or treatment.
Sources Handbook of Mineralogy
Other research findings
Sillimanite has the formula Al2SiO5 and is trimorphous with kyanite and andalusite, sharing the same composition but differing in structure.
Evidence grade BScope: Confirms the trimorphous relationship of the three Al2SiO5 polymorphs; the source gives no individual P-T fields.
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 sillimanite formation.
- The cited source only confirms that sillimanite is trimorphous with kyanite and andalusite; it gives no specific P-T stability fields, so those P-T statements are standard mineralogy rather than verbatim quotations.
- The source does not quantify the specific P-T conditions of sillimanite 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
- Sillimanite
GB/T 16552—2017 Table A.1 “Sillimanite” · IMA Mineral List 2026-07 “Sillimanite”
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
Sillimanite is Sillimanite; use "Sillimanite" for listings, and disclose any known treatments.
Evidence
- GB/T · Table A.1, row 矽线石 (Sillimanite)
What this means for you
Before buying, check the recommended listing name "Sillimanite" 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
Sillimanite — 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
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Sillimanite, p.76; §6.2 j (locator checked 2026-09-25)
- Fact checked on
- 2026-09-25
Sillimanite — 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
- CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §8 Annex C, Sillimanite, p.76; §6.2 k (locator checked 2026-09-25)
- 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
CleaningThe care entry for Sillimanite in the CIBJO Blue Book Official Gemstone Book (2022) states that it must not be cleaned ultrasonically. CIBJOCIBJO also states that treatments such as dyeing, oiling, resin, wax or plastic impregnation are not permanent; this conclusion applies only to dyed Sillimanite, in the treated state, which should be kept away from all solvents (including detergents of every kind), chemicals and heat. General careGeneral care for all gemstones is in the general care section of the materials index page.
This table scrolls sideways on narrow screens.
| Question | Matching entries |
|---|---|
| Can it go in an ultrasonic or steam cleaner? | care (cleaning) |
| Contact with acids, alkalis and household 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 |
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
- care (cleaning) §6.2 j
treated (Only after these treatments: dyeing)
Durability and wearing
Toughness
Tough in aggregate
VerifyNames, standards, technical facts, clauses and sources
Names
Besides Sillimanite, the name register records "Fibrolite" and "Sillimanite Cat's-eye", for which no restriction on use as a name is recorded (CIBJO Gemstone Book 2022 Annex 8 “Sillimanite Cat’s-eye”).
Chinese standard nameThe Chinese formal name for Sillimanite comes from GB/T 16552—2017 Table A.1; both the mineralogical name and the English name are Sillimanite, and Fibrolite is a trade name or synonym. Names in four languagesThe four-language names are given in Simplified Chinese, Traditional Chinese, English (Sillimanite) and Japanese (a transliteration and a kanji name), and the Japanese GSJ formal name is the kanji name. Recommended listing nameThe suggested listing name is Sillimanite. Institution usageAmong authority wordings, CIBJO lists Sillimanite, from the CIBJO Gemmological Laboratories Book 2024; the FTC source text has no wording for this name (checked); GIA and Gem-A have not been checked. Bodies without a recorded wording show Sillimanite'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.
| Name | Type | Matching | Use as a name | Basis |
|---|---|---|---|---|
| no restriction recorded (2) | ||||
| FibroliteEnglish | synonym | matched automatically | no restriction recorded | editorial ruling (no clause cited) |
| Sillimanite Cat's-eyeEnglish | narrower name (variety or subtype) | matched automatically | no restriction recorded | CIBJO Gemstone Book 2022 Annex 8 “Sillimanite Cat’s-eye” |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- 珪線石
- Chinese formal name
- 矽线石 (GB/T 16552—2017 Table A.1)
- Mineralogical name
- Sillimanite
- Trade names and synonyms
- Fibrolite (synonym) · Sillimanite Cat's-eye (narrower name (variety or subtype))
Four-language names
- 简体中文
- 矽线石
- 繁體中文
- 矽線石
- English
- Sillimanite
- 日本語
- シリマナイト／珪線石
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
What it is and how it's identified
Material facts for Sillimanite include: composition Al2SiO5, possibly containing Fe and other elements; crystalline, orthorhombic, with a prismatic or fibrous habit; Mohs hardness 6–7.5, with one perfect cleavage; density 3.14–3.27 g/cm³ (clause value 3.25, tolerance +0.02, −0.11, range worked out from that); refractive index 1.653–1.684 (clause value 1.659–1.680, tolerance +0.004, −0.006, range worked out from that); birefringence 0.015–0.021; optic character anisotropic, biaxial, optically positive, or an anisotropic aggregate; untreated Sillimanite has a vitreous to silky 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
Sillimanite — 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
Sillimanite — composition (chemistry): Al2SiO5, elements such as Fe may be contained.
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — composition (phase): sillimanite
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Sillimanite — structure (overall): crystalline
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — structure (crystal system): orthorhombic
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — structure (crystal habit): columnar or fibrous
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Durability
Sillimanite — Mohs hardness: 6–7.5
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — cleavage: perfect in one direction
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Physical properties
Sillimanite — density: 3.14–3.27 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives 3.25, with a stated tolerance of +0.02 / -0.11. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Sillimanite — optic character: biaxial, optically positive (anisotropic), or an 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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — refractive index: 1.653–1.684
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives 1.659–1.680, with a stated tolerance of +0.004 / -0.006. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — birefringence: 0.015–0.021
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — transparency: usually translucent to opaque, rarely transparent.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Sillimanite — pleochroism: in blue material, strong: colourless, light yellow and blue.
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — fluorescence (overall): blue: weak, red.
GB/T 16553—2017
UV fluorescenceredweak, blueDots 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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — spectrum (UV-visible): 410 nm weak absorption band; 441 nm weak absorption band; 462 nm weak absorption band.
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — spectrum (infrared): The mid-IR spectrum carries sillimanite's own diagnostic bands
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — optical effect (chatoyancy): seen
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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Sillimanite — magnification: gas-liquid inclusions, mineral inclusions, fibrous structure 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): §5.1.27 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
body colour2 sources compared
Sillimanite — body colour: white to grey, brown, green, rarely violetish to greyish blue.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Aragonite, Lazulite, Talc 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
Sillimanite — body colour: white to grey, brown and green; purple-blue to grey-blue (rare).
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 Iolite, Vesuvianite / Idocrase, Charoite 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): §5.1.27 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
How the sources relate
- CIBJO Gemmological Laboratories Book 2024 and GB/T 16553—2017
The two entries agree: white to grey, brown and green, and both note that violetish to greyish blue is rare. The CIBJO Gemmological Laboratories Book gives this under fibrolite, the fibrous form of sillimanite.
- CIBJO definitions
- chatoyancy
Quality factors
Sillimanite — quality factor (lustre): vitreous to silky
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): §5.1.27 (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): 1.668 / 3.21; Closest values: 1Kornerupine 1.673 / 3.31, 2Dioptase 1.681 / 3.3, 3Synthetic Jadeite 1.66 / 3.34, 4Euclase 1.663 / 3.06, 5Apatite 1.639 / 3.18
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
Testing and market
No synthetic counterpart of Sillimanite is on the market. The CIBJO laboratory protocol requires the easy cleavage of single crystals of Sillimanite to be checked in particular. Its note on testing methods states that the special optical effect of Sillimanite is the cat's-eye effect. Which tests the CIBJO laboratory protocol requires for Sillimanite, and what each method means, are set out in the protocol table on the laboratory testing page.
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: §6.1.75.
How far testing can go
Sillimanite — 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
Sillimanite — what the CIBJO laboratory protocol says to watch for: single crystal has easy cleavage
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Sillimanite — notes on test methods in the CIBJO laboratory protocol:
| Test method | What the protocol notes for it |
|---|---|
| Phenomena: | Cat’s-eye |
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
At clause level, Sillimanite is recorded in the CIBJO Gemmological Laboratories Book 2024 under two entries, Fibrolite and Sillimanite. The Fibrolite entry describes a material that is usually translucent to opaque and only rarely transparent, coloured white to grey, brown or green, and occasionally violetish to greyish blue. The cross-check for Fibrolite is that it is defined directly by CIBJO, and no identically named English entry for Fibrolite was found in this edition of the GB/T annex. The Sillimanite entry gives the definition as the mineral species sillimanite with IMA status G and states that the CIBJO wording is quoted in full under Clause-level definitions on this page; the cross-check is that it is defined directly by CIBJO and also appears in the GB/T annex. The IMA Mineral List entry records Sillimanite as Al2SiO5, IMA status G and 1824, cross-checked against the RRUFF/IMA master mineral list on the basis of public-domain data.
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| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Fibrolite | 7.2.1.88 | white to grey, brown, green, rarely violetish to greyish blue; usually translucent to opaque, rarely transparent. May show chatoyancy | Defined directly by CIBJO; no identically named English entry was found in this edition of the GB/T annex. |
| Sillimanite | 7.2.1.215 | white to grey, brown, green, rarely violetish to greyish blue; usually translucent to opaque, rarely transparent. May show chatoyancy | Defined directly by CIBJO; also present in the GB/T annex. |
| Sillimanite | IMA Mineral List entry | Sillimanite Al2SiO5 G 1824 | 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.
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| Page | Content | Status |
|---|---|---|
| Browsing family | Other silicate minerals | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Sillimanite 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.