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
Zoisite
A mineral species basic name listed in Annex A.1 of GB/T 16552-2017. Its colour varieties, set by colouring element, have common names: blue-violet tanzanite, manganese-pink thulite, and a rare chromium-green type. These are variety or trade names; the species is still zoisite.
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 Zoisite forms and what gives its colourFormation setting, process and timescale, each finding graded and sourced
- How to identify ZoisiteHow far lab testing can go and whether a synthetic exists
- Treatments and enhancements of Zoisite2 registered treatments: status, stability, how common they are and identification leads
- Caring for and wearing ZoisiteCleaning, heat, chemicals and light, as the cited sources give them; durability indicators and wearing advice
- Hardness, density and refractive index of ZoisiteEach value with its source and check date
- Zoisite 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 ZoisiteWhere the name comes from
- Listing and disclosing ZoisiteThe listing name to use; what must be disclosed before sale
- Standard clauses that define ZoisiteWhich 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
Zoisite belongs to the epidote group and is a calcium-aluminium sorosilicate, Ca2Al3(SiO4)(Si2O7)O(OH). Crystalline schists of medium metamorphic grade that developed regionally from igneous, sedimentary or metamorphic rocks rich in calcium are its typical host, and it is also found in blueschist-facies rocks and eclogites. Clinozoisite is dimorphous with zoisite, and tanzanite's host rock is the exceptional gem material occurring in Tanzania's Merelani Hills.
Scope: Covers the origin, composition and occurrence of zoisite as an epidote-group mineral species, and its role as the parent material defining the identity boundaries of tanzanite; does not address synthetic materials.
Sources Handbook of Mineralogy · CIBJO Gemstone Book 2022
Where it forms
Crystalline schists of medium metamorphic grade, regionally formed from igneous, sedimentary or metamorphic precursors relatively rich in calcium
Sources Handbook of Mineralogy
Blueschist-facies rocks together with eclogites
Sources Handbook of Mineralogy
The Merelani Hills (Lelatema Mountains), Tanzania, source of exceptional gem material
Sources Handbook of Mineralogy
How it forms, step by step
A calcium-rich protolith (igneous, sedimentary or metamorphic) supplies the Ca, Al and Si needed for zoisite.
Sources Handbook of Mineralogy
Under medium-grade regional metamorphism, zoisite crystallizes and grows within crystalline schists.
Sources Handbook of Mineralogy
In high-pressure settings such as eclogite and blueschist facies, zoisite may also occur as a stable mineral.
Sources Handbook of Mineralogy
At the Merelani Hills of Tanzania, zoisite forms facetable gem-quality blue-to-violet crystals.
Sources Handbook of Mineralogy
Link to appearance
Zoisite may be white, grey, greenish brown, greenish grey, pink, blue to purple, with a vitreous luster, pearly on cleavage, colorless to pink in thin section, and shows distinct pleochroism.
Sources Handbook of Mineralogy
Timescale
The sources do not state an absolute geological timescale for zoisite formation.
Sources Handbook of Mineralogy · CIBJO Gemstone Book 2022
Supporting findings
Zoisite is characteristic of crystalline schists of medium metamorphic grade that formed regionally from calcium-rich precursors; it also occurs in blueschist-facies rocks and eclogites.
Evidence grade BScope: Describes zoisite's metamorphic occurrence; excludes its commercial gem-variety settings.
Sources Handbook of Mineralogy
Tanzania's Merelani Hills, in the Lelatema Mountains some 40 km southeast of Arusha, are the source of exceptional gem-grade zoisite.
Evidence grade BScope: Describes one gem-grade locality for zoisite; zoisite is not restricted to this locality.
Sources Handbook of Mineralogy
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Africa
- Merelani Hills, TanzaniaIncludes tanzanite and chromium-colored green zoisite
Sources Gems & Gemology Winter 2000 · Handbook of Mineralogy
Asia
- Skardu area, KarakoramGem locality of the 1990s
Sources Gems & Gemology Winter 2000
Europe
- Prickler Halt, Eberstein, Carinthia, Austria
Sources Mindat: Zoisite
Seas and coasts
- WorldwideWidespread mineral; Mindat lists 1,602 localities
Sources Handbook of Mineralogy · Mindat: Zoisite
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
Zoisite honours Siegmund Zois, Baron von Edelstein (1747–1819), an Austrian patron of mineralogy who provided the first specimens.
Evidence grade BScope: This states only the origin of the name and does not establish the material's composition, locality, natural origin, or whether it was treated.
Sources Handbook of Mineralogy
Other research findings
Zoisite has the formula Ca2Al3(SiO4)(Si2O7)O(OH), belongs to the epidote group, and is dimorphous with clinozoisite.
Evidence grade BScope: Describes zoisite composition and dimorphism; does not extend to its gem variety tanzanite.
Sources Handbook of Mineralogy
Tanzanite is the blue-to-violet gem variety of zoisite; in CIBJO nomenclature the species is Zoisite, the variety is blue to violet, and the trade name is Tanzanite.
Evidence grade AScope: Defines the variety-to-species relationship between tanzanite and zoisite; does not treat tanzanite as an independent mineral species.
Sources Handbook of Mineralogy · CIBJO Gemstone Book 2022
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The sources state no absolute geological timescale for zoisite formation.
- The chromophores responsible for zoisite's color (e.g. Cr, V) are not explicitly attributed by the available sources.
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
- Zoisite
GB/T 16552—2017 Table A.1 “Zoisite” · IMA Mineral List 2026-07 “Zoisite”
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Heated / Heat-treated, Coated
Related:Disclosure and cautions
This page cannot answer
Natural? · Origin · Price
A lab report settles these; this wiki covers naming and disclosure.
Related:What this page can answer
Answer at a glance
Zoisite is Zoisite, Ca2Al3(SiO4)(Si2O7)O(OH); use "Zoisite" for listings, and disclose any known treatments.
Evidence
- GB/T · Table A.1, row 黝帘石 (Zoisite)
What this means for you
Before buying, check the recommended listing name "Zoisite" 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
care (cleaning)2 sources compared
Zoisite — 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
- Applies only to
- transparent zoisite in other colours
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Zoisite — care (cleaning): ultrasonic and steamer: avoid; note: avoid thermal shock.
Gems & Gemology 1987 (Martin)
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zoisite (Tanzanite) row, CLEANING column (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zoisite — care (setting): prong and bezel: use caution; channel: use extreme caution; flush and pavé: avoid; note: one perfect cleavage; brittle and abrades easily.
Gems & Gemology 1987 (Martin)
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zoisite (Tanzanite) row, SETTING column (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zoisite — care (repair): pickle pot and polishing: use extreme caution; jeweller's torch and thermal shock: avoid; note: avoid heat, as it fuses under the torch.
Gems & Gemology 1987 (Martin)
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zoisite (Tanzanite) row, REPAIR column (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Zoisite — care (display): heat in the display case, sunlight and artificial light: relatively safe.
Gems & Gemology 1987 (Martin)
- Treatment state
- untreated
Source & check 2026-09-26
- Source
- Martin, “Gemstone Durability: Design to Display”, Gems & Gemology, Summer 1987: pp.66–67 fold-out chart, Zoisite (Tanzanite) row, DISPLAY column (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.
Common care questions and matching entries
LightThe care conclusions for Zoisite come from the CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) and Martin's Gemstone Durability: Design to Display (Gems & Gemology, Summer 1987). CleaningThe CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) states that, in any treatment state and only for transparent Zoisite of other colours, it must not be cleaned ultrasonically. Martin, Gem DurabilityMartin states that for untreated Zoisite, both ultrasonic and steam cleaning should be avoided, as should thermal shock; in setting, prong and bezel settings need care, channel settings need extra care, and tension and pavé settings should be avoided, with a note that it has perfect cleavage in one direction, is brittle and wears easily; in repairs, pickling after soldering and polishing need extra care, the torch and thermal shock should be avoided, with a note to avoid heat as it melts under the torch; and in display, display-case heat, sunlight and artificial light are relatively safe.
This table scrolls sideways on narrow screens.
| Question | Matching entries |
|---|---|
| Can it go in an ultrasonic or steam cleaner? | transparent zoisite in other colours: care (cleaning); ultrasonic and steamer: avoid; note: avoid thermal shock |
| Heat and thermal shock | pickle pot and polishing: use extreme caution; jeweller's torch and thermal shock: avoid; note: avoid heat, as it fuses under the torch |
| Light and display | heat in the display case, sunlight and artificial light: relatively safe |
| Wearing limits (knocks, settings) | prong and bezel: use caution; channel: use extreme caution; flush and pavé: avoid; note: one perfect cleavage; brittle and abrades easily |
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
- transparent zoisite in other colours: care (cleaning) §6.2 j
untreated
- ultrasonic and steamer: avoid; note: avoid thermal shock
- prong and bezel: use caution; channel: use extreme caution; flush and pavé: avoid; note: one perfect cleavage; brittle and abrades easily
- pickle pot and polishing: use extreme caution; jeweller's torch and thermal shock: avoid; note: avoid heat, as it fuses under the torch
- heat in the display case, sunlight and artificial light: relatively safe
Durability and wearing
Toughness
Brittle
Treatments and identification leads
Registered treatmentsThe treatments registered for Zoisite are heating and coating. Values not givenBoth heating and coating have status treated, with stability and prevalence both marked "—", meaning the cited source gives no value, not "none". Identification cluesThe identification lead for heating is: some brownish zoisite turns violetish blue on heating, the colour is stable, and it is difficult to detect. The identification leads for coating are: magnification shows abnormal surface lustre and local peeling of the film, the film usually being blue; refractive index readings may be abnormal; infrared and Raman spectra show characteristic peaks of the film; and XRF and other compositional analysers can detect abnormal levels of foreign elements such as cobalt and titanium.
This table scrolls sideways on narrow screens.
| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| heatingStatus: treated | — | — | Optimization | — | See identification leads |
| coatingStatus: treated | — | — | Treatment | — | See identification leads |
Where each treatment acts (schematics): Heated / Heat-treated · Coated
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16553—2017; GB/T 16552—2017 Table B.1; JJA/AGL 2025
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
How lab reports word it
A general LMHC wording rule also covers Zoisite (Information Sheet #8): see the LMHC rule “When colour authenticity cannot be determined”.
VerifyNames, standards, technical facts, clauses and sources
Names
Standard and listing namesThe Chinese formal name for Zoisite is based on GB/T 16552—2017 Table A.1, and the suggested listing name is also Zoisite. Trade and mineralogical namesThe mineralogical name is Zoisite, with the chemical formula Ca2Al3(SiO4)(Si2O7)O(OH). Names in four languagesThe four-language names are given in Simplified Chinese, Traditional Chinese, English (Zoisite) and Japanese (a transliteration and a kanji name); the Japanese names are the entry's own, and the Japanese GSJ wording is not yet verified by this site. Institution usageAmong authority wordings, the CIBJO Gemmological Laboratories Book 2024 lists Zoisite; 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 the entry's own English name, which does not represent their position.
- GSJ (Japan) formal name
- ゾイサイト／灰簾石 (not yet checked for this body — the entry's own Japanese name is shown)
- Chinese formal name
- 黝帘石 (GB/T 16552—2017 Table A.1)
- Mineralogical name
- Zoisite, Ca2Al3(SiO4)(Si2O7)O(OH)
Four-language names
- 简体中文
- 黝帘石
- 繁體中文
- 黝簾石
- English
- Zoisite
- 日本語
- ゾイサイト／灰簾石
See also: Misleading and prohibited trade names · Supplementary name index
Classification
- Origin
- Natural materials
- Material domain
- Natural inorganic gem materials
- Browsing family
- Other silicate minerals
- Identity tier
- Mineral species
- Mineral chemical class
- Silicates
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
GB/T Table B.1The Zoisite (Tanzanite) row of GB/T 16552—2017 Annex B, Table B.1 lists: heating, which improves colour and is classed as optimization; and coating, which improves or changes lustre, colour and other aspects of appearance and is classed as treatment. The notes to Table B.1 and the definitions of each grade are on the Gem treatments page. JJA/AGL designationsThe table in the JJA/AGL (Japan) definitions and nomenclature, November 2025 revision, lists Zoisite under the species zoisite, with the colour recorded as transparent stones of other colours, and notes that the table lists a tier named untreated; how to read the JJA/AGL table is explained on the Gem treatments page.
GB/T 16552-2017, Annex B, Table B.1
Table B.1, row “Zoisite (Tanzanite)” (p.15):
This table scrolls sideways on narrow screens.
| Method | Effect | Category |
|---|---|---|
| Heating | Improves colour | Optimization |
| Coating | Improves or changes lustre, colour and other aspects of appearance | Treatment |
What Table B.1 is, and how the “see 5.4.1” grades are defined: see the GB/T 16552: optimization vs treatment page.
JJA/AGL (Japan) table of principal gem names, 2025
This table scrolls sideways on narrow screens.
| Gem name | Species | Colour | Listed in the table | Notes |
|---|---|---|---|---|
| [colour] Zoisite | Zoisite | transparent stones of other colours | an untreated tier is listed |
JJA/AGL definitions and nomenclature (2025 revision), table of principal gem names, p.14
How to read the JJA/AGL table: see the Gem treatments page.
What it is and how it's identified
Zoisite has the composition Ca2Al3(Si2O7)(SiO4)O(OH), possibly containing V, Cr, Mn and other elements, phase zoisite; crystalline, orthorhombic, with a prismatic or tabular-prismatic habit. Mohs hardness 6–7, with one perfect cleavage. Density 3.1–3.45 g/cm³, worked out from the clause value 3.35 and tolerance of +0.10, −0.25; refractive index 1.686–1.705, worked out from the clause value 1.691–1.700 and tolerance of ±0.005; birefringence 0.008–0.013; optic character anisotropic, biaxial, optically positive; transparency transparent to opaque. Untreated Zoisite has a vitreous lustre, strong trichroic pleochroism and no fluorescence. In the UV-visible spectrum, blue material shows absorption peaks at 595nm and 528nm, and yellow material an absorption peak at 455nm; the mid-infrared region shows the characteristic infrared absorption bands of zoisite.
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
Zoisite — 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
Zoisite — composition (chemistry): Ca2Al3 (Si2O7) (SiO4) O (OH), elements such as V,Cr and Mn 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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — composition (phase): zoisite
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Structure
Zoisite — 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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — 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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — structure (crystal habit): columnar or platy-columnar
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Durability
Zoisite — Mohs hardness: 6–7
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — 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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Physical properties
Zoisite — density: 3.1–3.45 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives 3.35, with a stated tolerance of +0.10 / -0.25. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Optical
Zoisite — optic character: biaxial, optically positive (anisotropic)
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — refractive index: 1.686–1.705
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite gives 1.691–1.700, with a stated tolerance of ±0.005. The range shown here is worked out from that.
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — birefringence: 0.008–0.013
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — transparency: transparent to opaque.
CIBJO Gemmological Laboratories Book 2024
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Zoisite — pleochroism: trichroism, strong. In blue tanzanite the three colours are blue, purple-red and green-yellow; brown stones show green, purple and light blue; yellow-green stones show dark blue, yellow-green and purple.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
Source & check 2026-09-22
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.20 (locator checked 2026-09-22)
- Fact checked on
- 2026-09-22
Zoisite — 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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — spectrum (UV-visible): blue: 595 nm absorption peak; 528 nm absorption peak; yellow: 455 nm absorption peak.
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — spectrum (infrared): Mid-IR absorption follows the pattern typical of zoisite
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — optical effect (chatoyancy): seen; rare
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — magnification: gas-liquid inclusions, growth striations, included minerals such as actinolite, graphite and staurolite (grenatite).
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
body colour2 sources compared
Zoisite — body colour: Blue to violet, green, pink, brown.
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- untreated
- Qualification
In chapter 7 of the CIBJO Gemmological Laboratories Book, the colour descriptions of Apatite, Benitoite, Sapphire and other entries also name blue or a bluish colour.
- General note
- colour alone is not identity
Source & check 2026-09-22
- Source
- Fact checked on
- 2026-09-22
Zoisite — body colour: Tanzanite is blue, purple-blue or blue-purple; other zoisite is brown, yellow-green or pink.
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 Fluorite, Apatite, Cat’s-eye and other variety clauses also name blue or a bluish colour.
- General note
- colour alone is not identity
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.20 (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
Both list blue to violet, green (yellow-green in GB/T 16553—2017), pink and brown. GB/T 16553—2017 assigns the blue, purplish blue to bluish purple colours to tanzanite.
- CIBJO definitions
- chatoyancy
Quality factors
Zoisite — quality factor (lustre): vitreous
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): §5.1.20 (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Geological occurrence
Zoisite — occurrence (formation): Green zoisite usually occurs as an aggregate, growing together with ruby crystals and hornblende.
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): §5.1.20 Additional notes (locator checked 2026-09-28)
- 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): 1.696 / 3.28; Closest values: 1Axinite 1.683 / 3.31, 2Hydrogrossular 1.7 / 3.35, 3Enstatite 1.712 / 3.31, 4Fei Cui / Jadeite Jade 1.683 / 3.35, 5Kornerupine 1.673 / 3.31
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
Identification leads for Zoisite include: for heat-treated Zoisite, some brownish Zoisite turns violetish blue on heating, with a stable colour that is difficult to detect; for coated Zoisite, the surface lustre is abnormal under magnification, the coating layer may peel locally and is mostly blue, the refractive index may give abnormal readings, infrared and Raman spectra can detect characteristic peaks of the coating, and compositional analysers such as XRF can find abnormal levels of foreign elements such as cobalt and titanium. The identification leads for both heat treatment and coating are cited from GB/T 16553—2017, which can only be used as a reference for Zoisite and does not govern it directly. The CIBJO Blue Book (Official Gemstone Book 2022) records that no synthetic counterpart of Zoisite is on the market. The CIBJO Gemmological Laboratories Book 2024 requires heat treatment, clarity enhancement and coating to be checked in particular, with a note that EDXRF compositional analysis is used for cobalt coating.
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: §6.1.92.
How far testing can go
Zoisite that has undergone heating can be identified by the following features: Heating some brown-tinted zoisite produces a purple-blue colour; the colour is stable and the treatment is not easy to detect.
GB/T 16553—2017
- Treatment state
- treated
- Does this standard apply
- can be followed as a reference only
- Treatment
- heating
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.20 (heating) (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite that has undergone coating can be identified by the following features: Under magnification the surface luster is abnormal and the film, often blue, can be seen peeling off in places; refractive index readings may be abnormal; infrared and Raman spectra show characteristic peaks of the film.
Compositional analysis (such as XRF) detects abnormal amounts of foreign elements such as cobalt and titanium.
GB/T 16553—2017
- Treatment state
- treated
- Does this standard apply
- can be followed as a reference only
- Treatment
- coating
Source & check 2026-09-21
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.20 (coating) (locator checked 2026-09-21)
- Fact checked on
- 2026-09-21
Zoisite — 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
Zoisite — what the CIBJO laboratory protocol says to watch for: heat treatment, clarity enhancement, coating
CIBJO Gemmological Laboratories Book 2024
- Treatment state
- any treatment state
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Zoisite — notes on test methods in the CIBJO laboratory protocol:
| Test method | What the protocol notes for it |
|---|---|
| EDXRF chemistry: | Cobalt coating |
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
The clause-level definition of Zoisite is registered in the CIBJO Gemmological Laboratories Book 2024 under the term Zoisite, defined as blue to violet, green, pink, brown; transparent to opaque. The cross-check result is that it is defined directly by CIBJO and also appears in the GB/T annex. The IMA Mineral List entry records it as Zoisite, with the chemical formula Ca2Al3(Si2O7)(SiO4)O(OH), cross-checked against the RRUFF/IMA master mineral list (public domain data).
This table scrolls sideways on narrow screens.
| Term | Clause | Definition | Cross-check |
|---|---|---|---|
| Zoisite | 7.2.1.267 | Blue to violet, green, pink, brown; transparent to opaque | Defined directly by CIBJO; also present in the GB/T annex. |
| Zoisite | IMA Mineral List entry | Zoisite Ca2Al3(Si2O7)(SiO4)O(OH) G 1805 | 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 | Other silicate minerals | Live |
| Treatments recorded for this material | Heated / Heat-treated, Coated | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Zoisite 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.