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
Achroite
The colorless variety of tourmaline. It is extremely rare and the risk of imitations is high; imitations must be labelled with an equally prominent qualifier right next to the stone name. 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 Achroite 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 AchroiteHow far lab testing can go
- Treatments and enhancements of AchroiteThe enhancements and treatments the GB/T and JJA/AGL tables list
- Caring for and wearing AchroiteCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of AchroiteEach value with its source and check date
- Achroite 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?
- Listing and disclosing AchroiteThe listing name to use; what must be disclosed before sale
- Standard clauses that define AchroiteWhich 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
Colourless tourmaline is not an independent mineral species but the colourless end of the tourmaline colour range; elbaite can be green, blue, yellow, pink to red, or colourless (or zoned), so colourless tourmaline is largely elbaite. Colourlessness generally corresponds to very low amounts of chromophores (Fe, Ti, Mn, Cu, Cr, V) and the absence of an effective colour centre, but the cited sources do not directly define the cause of colourlessness in tourmaline and this attribution is an inference. Like other elbaite, the parent material forms in pockets of granite-bearing pegmatites.
Scope: Applies to explaining the colouration and occurrence of natural colourless tourmaline (mostly elbaite); the attribution of the cause of colourlessness is inferred, and it is not applicable to identifying the species or locality of a specific sample.
Sources GIA Tourmaline Description · G&G Summer 2025
Where it forms
Granite-bearing pegmatites; elbaite occurs in pegmatite pockets.
Sources GIA Tourmaline Description · G&G Summer 2025
One pegmatite body (or one pocket) can yield crystals of very different colours, including colourless or zoned material.
Sources GIA Tourmaline Description · G&G Summer 2025
How it forms, step by step
The pegmatite's residual fluid crystallises and elbaite grows.
Sources GIA Tourmaline Description · G&G Summer 2025
Where chromophore elements such as Fe, Mn, Cu, Cr, and V are very low and no effective colour centre forms, the crystal is colourless.
Sources GIA Tourmaline Description · G&G Summer 2025
Trace elements can vary during growth, producing zoned or partly colourless crystals.
Sources GIA Tourmaline Description · G&G Summer 2025
Link to appearance
A colourless appearance corresponds to very low chromophore content, but appearance cannot fix the species or confirm colourless tourmaline, nor exclude treatment or synthesis.
Sources GIA Tourmaline Description
Timescale
The cited sources give no absolute timescale for colourless tourmaline formation.
Sources GIA Tourmaline Description · G&G Summer 2025
Related base materials
- Tourmaline group (elbaite): colourless end-member of the elbaite colour range
Supporting findings
Elbaite forms in granite-bearing pegmatites (pockets), and different pockets of one pegmatite body can yield tourmaline of very different colours, including colourless.
Evidence grade AScope: The general pegmatite setting; it gives no abundance or proportion of colourless material by locality.
Sources GIA Tourmaline Description · G&G Summer 2025
Overall, colourless tourmaline is elbaite grown in pegmatites that is colourless for lack of chromophores, sharing its origin with coloured tourmaline and differing only in trace-element content.
Evidence grade BScope: A synthesis treating “colourless = chromophore-poor” as an inference; it cannot be used to identify a specific specimen.
Sources GIA Tourmaline Description
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
North America
- Newry, Maine, United StatesA bicolor cat's-eye tourmaline from Newry with a near-colorless (achroite) zone; no production statement
Sources Gems & Gemology Summer 2015
South America
- BrazilLocality recorded for a faceted achroite in GIA's Gübelin collection
Sources GIA Gübelin Gem Project
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
Synthesis: colourlessness in tourmaline reflects very low Fe, Ti, Mn, Cu, Cr, and V content and the absence of an effective colour centre, since the cited source attributes tourmaline colour to these trace elements and to (possibly radiation-caused) colour centres.
Evidence grade BScope: An inference from the general colouring mechanism; the source does not directly define colourlessness in tourmaline and gives no threshold values.
Sources GIA Tourmaline Description
Other research findings
Elbaite occurs in many colours, including colourless; its stones may be green, blue or yellow, pink through red, colourless, or else zoned.
Evidence grade AScope: An enumeration of the elbaite colour range; it does not make colourless tourmaline an independent variety or species.
Sources GIA Tourmaline Description
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The cited sources give no absolute timescale for colourless tourmaline formation.
- That colourlessness arises from chromophore-poor composition and no effective colour centre is an inference; the cited sources do not directly define its cause.
- No quantitative criterion or per-locality abundance of colourless tourmaline 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
- Achroite (colourless tourmaline)
16 CFR Part 23 §23.25(b)
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Heated / Heat-treated (via parent material), Filled / Fracture-filled (via parent material), Dyed (via parent material), Irradiated (via parent material), Coated (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
Extremely rare, with a high risk of imitations.
Evidence
What this means for you
Before buying, check the recommended listing name "Achroite (colourless tourmaline)" 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
The item-by-item care advice that the GIA Care and Cleaning Guide gives for the whole class, and so for Achroite, is set out in full under care on the Tourmaline entry.
Care
Each row's “Source & check” expands to the full source; the date beside it is the fact check date.
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 | — | — |
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
| Dyeing | — | — | Treatment | — | — |
| Irradiation | — | — | Treatment | — | — |
| Coating | — | — | Treatment | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Tourmaline)
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 GB/T 16552—2017 naming counterpart for Achroite is tourmaline (Table A.1); the name Achroite itself is not listed in the standard, and the suggested listing name is Achroite. Names in four languagesNames are registered in four languages: Simplified Chinese, Traditional Chinese, English (Achroite) and Japanese. The Japanese name shown is the entry's own; the wording used by the GSJ (Japan) for Achroite is not yet verified by this site. Institution usageOn authority wording, CIBJO records Achroite (CIBJO Gemmological Laboratories Book 2024); the FTC text on file has no wording for this name (checked); GIA and Gem-A are unchecked. Bodies without a recorded wording show the entry's own English name, which does not represent their position.
- GSJ (Japan) formal name
- アクロアイト／無色電気石 (not yet checked for this body — the entry's own Japanese name is shown)
- GB/T naming counterpart (this name is not in the standard)
- 碧玺 (GB/T 16552—2017 Table A.1)
- Mineralogical name
- Colourless tourmaline variety
Four-language names
- 简体中文
- 无色碧玺
- 繁體中文
- 無色碧璽
- English
- Achroite
- 日本語
- アクロアイト／無色電気石
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural inorganic gem materials
- Browsing family
- Tourmaline-supergroup minerals and gem varieties
- Identity tier
- Mineral / gemstone variety
- Mineral chemical class
- Silicates
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
Treatments for Achroite are classified against GB/T 16552—2017, Annex B, Table B.1: this site applies the “Tourmaline” row of Table B.1 to Achroite, and the standard does not list Achroite directly. On that basis, heat treatment is an optimization, filling is marked as graded, and dyeing, irradiation and coating are all treatments. How filling is graded and what Table B.1 is are explained on this site's Gem treatments page; the full row, including the effect notes, is on the Tourmaline entry.
GB/T 16552-2017, Annex B, Table B.1
Under the “Tourmaline” row of Table B.1: Heating Optimization; Filling Graded — see §5.4.1, Table 1; Dyeing Treatment; Irradiation Treatment; Coating Treatment. The full row, with the effect column, is on the Tourmaline 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
Achroite's composition (phase) is the tourmaline group. Untreated, its body colour is colourless; in Chapter 7 of CIBJO, the colour descriptions for entries such as crystal opal, colourless beryl and rock crystal also mention colourless. The following values are registered for tourmaline (the whole mineral group), not measured on Achroite itself: crystalline, trigonal; Mohs hardness 7–8, no cleavage; density 2.46–3.26 g/cm³, worked out from the cited clause's 3.06 with a stated tolerance of +0.20, −0.60; optic character anisotropic, uniaxial, optically negative; refractive index 1.615–1.655, worked out from the cited clause's 1.624–1.644 with a stated tolerance of +0.011, −0.009; birefringence 0.018–0.04, the overall value, as the clause also gives finer sub-ranges; untreated, pleochroism is moderate to strong, in darker and lighter shades of the body colour, and the quality factor (lustre) is vitreous.
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”.
Luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for tourmaline (the whole mineral group), so they are not repeated on the Achroite page; see the material facts on the Tourmaline entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Achroite (how to read class-level values).
Definition
Achroite — composition (phase): tourmaline group
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Achroite — structure (overall): crystalline
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Achroite — structure (crystal system): trigonal
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Achroite — structure (crystal habit): rounded trigonal prisms or more complex ditrigonal prism-and-pyramid combinations; the crystal faces are distinctly striated lengthwise.
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Achroite — Mohs hardness: 7–8
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
- tourmaline (the whole mineral group)
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Achroite — cleavage: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Achroite — density: 2.46–3.26 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
- Qualification
The clause we cite gives 3.06, with a stated tolerance of +0.20 / -0.60. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Achroite — optic character: uniaxial, optically negative (anisotropic)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Achroite — refractive index: 1.615–1.655
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
- Qualification
The clause we cite gives 1.624–1.644, with a stated tolerance of +0.011 / -0.009. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Achroite — birefringence: 0.018–0.04
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
- General note
- the clause has finer ranges
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Achroite — pleochroism: moderate to strong, in lighter and deeper shades of the body colour.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Achroite — optical effect (chatoyancy): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Achroite — optical effect (colour change): seen; rare
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Achroite — body colour: Colourless.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Crystal Opal, Goshenite, Rock Crystal and other entries also name colourless.
- General note
- colour alone is not identity
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
- CIBJO definitions
- chatoyancy, colour change
Quality factors
Achroite — quality factor (lustre): vitreous
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- tourmaline (the whole mineral group)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (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): 1.635 / 2.86; Closest values: 1Prehnite 1.625 / 2.88, 2Larimar 1.62 / 2.82, 3Datolite 1.646 / 2.95, 4Danburite 1.633 / 3, 5Sugilite 1.61 / 2.77
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 Achroite under “Tourmaline” (§6.1.86): see identification on the Tourmaline entry; the required tests are listed on the CIBJO laboratory protocol table for Tourmaline.
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
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Achroite | 7.2.1.1 | Colourless variety of tourmaline | Defined directly by CIBJO; no identically named English entry was found in this edition of 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.
- GIA – Gemological Institute of America (United States). Gem Encyclopedia.
- Gem-A – The Gemmological Association of Great Britain (United Kingdom).
- eCFR (United States). 16 CFR § 23.25 — Misuse of the words “ruby,” “sapphire,” “emerald,” “topaz,” “stone,” “birthstone,” “gem,” “gemstone,” etc. In: 16 CFR Part 23 — Guides for the Jewelry, Precious Metals, and Pewter Industries.
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.
Related-entry tree for Tourmaline on this site: 12 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Achroite) is marked.
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Tourmaline-supergroup minerals and gem varieties | Live |
| Treatments recorded for this material | Heated / Heat-treated (via parent material), Filled / Fracture-filled (via parent material), Dyed (via parent material), Irradiated (via parent material), Coated (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Achroite 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.