On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Mineral / gemstone variety · Natural identity; treatment status unknown
Chiastolite
A variety of Andalusite whose inclusions form a cross pattern; its GB/T 16552-2017 Appendix A.1 name is Chiastolite, and it is not a separate mineral species. 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 Chiastolite forms and what gives its colourFormation setting, process and timescale; where its colour and optical effects come from, each finding graded and sourced
- How to identify ChiastoliteHow far lab testing can go
- Treatments and enhancements of ChiastoliteThe enhancements and treatments the GB/T and JJA/AGL tables list
- Caring for and wearing ChiastoliteDurability indicators and wearing advice
- Hardness, density and refractive index of ChiastoliteEach value with its source and check date
- Chiastolite 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 ChiastoliteWhere the name comes from
- Listing and disclosing ChiastoliteThe listing name to use; what must be disclosed before sale
- Standard clauses that define ChiastoliteWhich 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
Chiastolite is a variety of andalusite, not an independent species; it is characterized by carbonaceous/clay inclusions arranged in a cross pattern. Andalusite is the Al2SiO5 phase stable at lower-pressure conditions, one of the three trimorphous Al2SiO5 polymorphs (with kyanite and sillimanite); it is a product of contact metamorphism of argillaceous sediments and also occurs in regionally metamorphosed schists. CIBJO nomenclature lists 'Chiastolite' as a variety name related to andalusite. The formation content rests on the parent andalusite; note that the cited authoritative sources do not describe the mechanism of the cross pattern (arrangement of carbonaceous inclusions).
Scope: Applies to the formation summary of chiastolite (the cross-patterned variety of andalusite); formation content follows the parent material andalusite, and evidence for the cross-pattern mechanism is lacking.
Sources Handbook of Mineralogy · G&G Summer 2023
Where it forms
Contact-metamorphic settings of argillaceous sediments; also regionally metamorphosed schists.
Sources Handbook of Mineralogy
How it forms, step by step
Under contact (or regional) metamorphism, aluminous pelitic protoliths undergo metamorphic reactions.
Sources Handbook of Mineralogy
Andalusite, the lower-pressure-stable Al2SiO5 phase, forms.
Sources Handbook of Mineralogy
Carbonaceous/clay inclusions are trapped during growth, forming the cross pattern (mechanism not described in the cited authoritative sources).
Sources Handbook of Mineralogy
Link to appearance
The cross pattern of chiastolite comes from the arrangement of carbonaceous/clay inclusions; appearance alone cannot determine species or origin.
Sources Handbook of Mineralogy
Timescale
The sources in this record give no absolute age or growth duration for chiastolite or andalusite.
Sources Handbook of Mineralogy · CIBJO Gemstone Book 2022 · G&G Summer 2023
Related base materials
- andalusite: Chiastolite is the variety of andalusite in which carbonaceous/clay inclusions form a cross pattern; its parent material is andalusite
Supporting findings
The parent andalusite of chiastolite is a product of contact metamorphism of argillaceous sediments and also occurs in regionally metamorphosed schists.
Evidence grade BScope: Describes the metamorphic occurrence of the parent andalusite; chiastolite is its carbonaceous-inclusion variety.
Sources Handbook of Mineralogy
Andalusite (the parent of chiastolite) is the Al2SiO5 phase stable at lower-pressure conditions.
Evidence grade AScope: Describes relative stability; no absolute temperature.
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Asia
- Hunan, China
Sources Mindat: Chiastolite
- Xixia County, Henan, China
Sources Mindat: Chiastolite
Europe
- Northern SpainKnown from the late 1500s as 'cross stone', popular with pilgrims in northern Spain
Sources Mindat: Chiastolite
- Boal, Asturias, Spain
Sources Mindat: Chiastolite
North America
- Lancaster, Worcester County, Massachusetts, United States
Sources Mindat: Chiastolite
Oceania
- Bimbowrie, South Australia, Australia
Sources Mindat: Chiastolite
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
Andalusite's colour may be pink, violet, yellow, green, white, or gray, and colorless to pink or green in thin section.
Evidence grade BScope: Describes the colour range; not the origin of the cross pattern.
Sources Handbook of Mineralogy
Where the name comes from
The etymology given here belongs to the parent mineral andalusite: the name andalusite is named after an occurrence in the Andalusia region, Spain. This is not the origin of the trade name “chiastolite”; the source gives no etymology for that name.
Evidence grade BScope: The etymology belongs to the parent mineral and does not establish the composition, locality, naturalness, or treatment of the material denoted by the trade name.
Sources Handbook of Mineralogy
Other research findings
Andalusite is one of the three trimorphous Al2SiO5 polymorphs (with kyanite and sillimanite); its stability field corresponds to lower-pressure conditions.
Evidence grade BScope: Polymorphic relation and relative stability; exact P-T follows the phase diagram.
Sources Handbook of Mineralogy · G&G Summer 2023
CIBJO nomenclature lists 'Chiastolite' as a variety/name related to andalusite (listed as a variety in the table, commonly 'no treatment').
Evidence grade AScope: Defines it as a listed variety name; does not claim it is an independent species.
Sources CIBJO Gemstone Book 2022
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- Chiastolite is a variety name of andalusite, not an independent species; formation rests on the parent andalusite.
- None of the authoritative sources consulted describes how the cross pattern (the arrangement of carbonaceous inclusions) forms.
- No absolute age or growth duration is given.
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
- Chiastolite
GB/T 16552—2017 Table A.1 “Chiastolite” · IMA Mineral List 2026-07 “Andalusite”
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Heated / Heat-treated (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
Chiastolite is Cross-pattern andalusite variety; use "Chiastolite" for listings, and disclose any known treatments.
Evidence
- GB/T · Table A.1, row 空晶石 (Chiastolite)
What this means for you
Before buying, check the recommended listing name "Chiastolite" 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
No institutional care guidance is registered for this material yet; below are its durability indicators and general guidance.
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
Brittle
Fracture
Uneven to subconchoidal
Sources Handbook of Mineralogy
Daily wear
Andalusite ranks 6.5–7.5 on the Mohs scale, brittle with a good {110} cleavage; daily wear should avoid impact and abrasion that may split it along cleavage.
Care
As a brittle material with cleavage, clean gently with warm, mild soapy water and a soft cloth; avoid ultrasonic and steam cleaners, sudden temperature changes, and impact or rubbing against hard objects.
General guidance: LumaLark's general guidance inferred from the material's properties (hardness, toughness, cleavage); not text from the cited source, and not a guarantee for any specific piece.
Scope: This field describes the general properties of the material and does not constitute a durability or safety guarantee for any specific finished product; the durability of treated (filled/dyed/coated) or composite pieces must be assessed separately.
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.
| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| Heating | — | — | Optimization | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Andalusite)
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
Standard and listing namesThe Chinese formal name for Chiastolite comes from GB/T 16552—2017 Table A.1, and the suggested listing name is Chiastolite. Trade and mineralogical namesThe mineralogical name is Cross-pattern andalusite variety. Names in four languagesNames are given in Simplified Chinese, Traditional Chinese, English (Chiastolite) and Japanese. Institution usageOn authority wording, CIBJO includes Chiastolite, based on CIBJO Gemmological Laboratories Book 2024, and this site records only the CIBJO wording; the FTC text contains no wording for this name, and this has been checked; GIA and Gem-A are unchecked. For bodies without a recorded wording, the name shown is the entry's own English name for Chiastolite, which does not represent the position of those bodies. Japanese namesThe entry has its own Japanese name for Chiastolite, and the wording used by GSJ (Japan) for this name is not yet verified by this site.
- GSJ (Japan) formal name
- キアストライト／空晶石 (not yet checked for this body — the entry's own Japanese name is shown)
- Chinese formal name
- 空晶石 (GB/T 16552—2017 Table A.1)
- Mineralogical name
- Cross-pattern andalusite variety
Four-language names
- 简体中文
- 空晶石
- 繁體中文
- 空晶石
- English
- Chiastolite
- 日本語
- キアストライト／空晶石
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 / gemstone variety
- Mineral chemical class
- Silicates
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
GB/T 16552-2017, Annex B, Table B.1
Under the “Andalusite” row of Table B.1: Heating Optimization. The full row, with the effect column, is on the Andalusite page.
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
Chiastolite is andalusite with a black cross inside, and its composition (phase) is andalusite. Registered for andalusite as a whole mineral species: the structure is crystalline, orthorhombic, with prismatic crystals; Mohs hardness is 7–7.5 and cleavage is one moderate direction; density is 3.13–3.21 g/cm³ (the cited clause gives 3.17 with a tolerance of ±0.04, from which the range is derived); optical character is anisotropic, biaxial negative; refractive index is 1.629–1.648 (the cited clause gives 1.634–1.643 with a tolerance of ±0.005, from which the range is derived); birefringence is 0.007–0.013. Also registered for andalusite as a whole, in the untreated state, pleochroism is strong trichroism in brownish yellowish green, brownish orange and brownish red, and lustre (quality factor) is vitreous. In the untreated state, magnification shows black carbonaceous inclusions arranged in a cross; CIBJO registers the transparency of Chiastolite as opaque.
Registered material facts
Each row carries its own source and check date and can be cited on its own; “—” means the cited source gives no value, not “none”.
Chemical composition, long-wave UV luminescence, short-wave UV luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for andalusite (the whole mineral species), so they are not repeated on the Chiastolite page; see the material facts on the Andalusite entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Chiastolite (how to read class-level values).
Definition
Chiastolite: andalusite with a black cross inside
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): §5.1.26 Colour · Chiastolite (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
Chiastolite — composition (phase): andalusite
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Chiastolite — structure (overall): crystalline
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Chiastolite — structure (crystal system): orthorhombic
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Chiastolite — structure (crystal habit): columnar
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Chiastolite — Mohs hardness: 7–7.5
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
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Chiastolite — cleavage: moderate in one direction
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Chiastolite — density: 3.13–3.21 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
- Qualification
The clause we cite gives 3.17, with a stated tolerance of ±0.04. The range shown here is worked out from that.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Chiastolite — optic character: biaxial, optically negative (anisotropic)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Chiastolite — refractive index: 1.629–1.648
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
- Qualification
The clause we cite gives 1.634–1.643, with a stated tolerance of ±0.005. The range shown here is worked out from that.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Chiastolite — birefringence: 0.007–0.013
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Chiastolite — transparency: opaque.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Chiastolite — pleochroism: Trichroism is strong: brownish orange, brownish red and brownish yellow-green.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Chiastolite — magnification: black carbonaceous inclusions arranged in a cross
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 Magnification (locator checked 2026-09-28)
- Fact checked on
- 2026-09-26
Chiastolite — body colour: White, grey, yellowish.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Magnesite, Howlite, Opal 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
Quality factors
Chiastolite — quality factor (lustre): vitreous
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- andalusite (the whole mineral species)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.26 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
This material (RI / SG midpoints): 1.639 / 3.17; Closest values: 1Lazulite 1.627 / 3.12, 2Sillimanite 1.668 / 3.21, 3Actinolite 1.627 / 3.03, 4Euclase 1.663 / 3.06, 5Danburite 1.633 / 3
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
The CIBJO laboratory protocol covers Chiastolite under “Andalusite” (§6.1.6): see identification on the Andalusite entry; the required tests are listed on the CIBJO laboratory protocol table for Andalusite.
How far testing can go
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
Clause-level definitions
Chiastolite has a direct definition in the CIBJO Gemmological Laboratories Book 2024, registered under the term Chiastolite; the definition states that the mineral species is andalusite and the mineral or gem variety is chiastolite, with the CIBJO wording quoted in full under Clause-level definitions on this page. The cross-check shows that it is defined directly by CIBJO and also appears in the GB/T annex.
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Chiastolite | 7.2.1.48 | White, grey, yellowish, opaque variety of andalusite, usually showing a blackish cross, caused by carbonaceous inclusions | Defined directly by CIBJO; also present in the GB/T annex. |
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 | Other silicate minerals | Live |
| Treatments recorded for this material | Heated / Heat-treated (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Chiastolite 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.