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
Tourmaline Cat’s-eye
Tourmaline showing a cat’s-eye effect. Under GB/T 16552 §5.3.1, the name is formed by adding "cat’s-eye" after the basic 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 Tourmaline Cat’s-eye 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 Tourmaline Cat’s-eyeHow far lab testing can go and whether a synthetic exists
- Treatments and enhancements of Tourmaline Cat’s-eye2 registered treatments: status, stability, how common they are and identification leads
- Caring for and wearing Tourmaline Cat’s-eyeCleaning, heat, chemicals and light, as the cited sources give them
- Hardness, density and refractive index of Tourmaline Cat’s-eyeEach value with its source and check date
- Tourmaline Cat’s-eye in English, Chinese and Japanese; national standard namesNames in four languages, the GB/T standard name and the suggested listing name; and: Has any of GIA, FTC, CIBJO or Gem-A put a name for it on record here?
- Listing and disclosing Tourmaline Cat’s-eyeThe listing name to use; what must be disclosed before sale
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
Tourmaline cat's-eye means tourmaline that shows chatoyancy — a slender band of light reflected from a cabochon-cut gemstone, moving across it as the stone turns, produced by parallel needle inclusions or fibrous textures. In tourmaline the cause is the many thin, tube-like inclusions that grow naturally within the stone; since these are coarser than the ones in cat's-eye chrysoberyl, the tourmaline eye looks softer and more diffuse. Cutting the stone en cabochon is needed to bring the effect out. Tourmaline cat's-eye is a variety name based on an optical effect, not an independent species.
Scope: Applies at the level of the variety name for natural tourmaline showing a cat's-eye effect; the parent mineral species and whether it has been treated must be determined separately.
Sources G&G Summer 2025 · GIA Tourmaline Description
Where it forms
The parent tourmaline grows in granitic pegmatites, and during growth forms parallel, thin, tube-like inclusions
Sources G&G Summer 2025 · GIA Tourmaline Description
How it forms, step by step
A tourmaline crystal grows in a pegmatite, trapping numerous thin, tube-like inclusions parallel to one direction
Sources G&G Summer 2025 · GIA Tourmaline Description
The parallel needle/tube inclusions scatter incident light
Sources G&G Summer 2025 · GIA Tourmaline Description
The gem is cut as a cabochon; the domed surface acts as a lens, focusing the scattered light into a bright band that moves as the stone rotates—the cat's-eye effect
Sources G&G Summer 2025 · GIA Tourmaline Description
Link to appearance
The cat's-eye effect arises from parallel needle/tube inclusions together with the cabochon cut; the effect alone cannot establish the species, origin or treatment.
Sources G&G Summer 2025 · GIA Tourmaline Description
Timescale
The cited texts give no timescale for inclusion formation or crystal growth in cat's-eye tourmaline.
Sources G&G Summer 2025 · GIA Tourmaline Description
Related base materials
- Tourmaline: Tourmaline cat's-eye is the variety name for tourmaline showing the cat's-eye effect (chatoyancy); an optical effect does not constitute an independent mineral species
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
South America
- BrazilA suite of cat's-eye tourmalines all from Brazil
Sources GIA Tourmaline Quality Factors
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
Chatoyancy is a slender band of light reflected from a cabochon-cut gemstone, travelling across it as the stone turns; it is caused by parallel needle inclusions or by fibrous textures, and the stone has to be cut en cabochon for the effect to appear.
Evidence grade AScope: The general mechanism/definition of chatoyancy; not specific to tourmaline parameters.
The cat's-eye effect in tourmaline is caused by numerous thin, tube-like inclusions formed naturally during growth; because they are coarser than those in cat's-eye chrysoberyl the eye is softer and more diffused, and the stone must be cut as a cabochon.
Evidence grade BScope: Mechanism and appearance of the tourmaline cat's-eye; no origin or treatment inference.
Sources GIA Tourmaline Description
Other research findings
Synthesis: tourmaline cat's-eye is an effect-based variety name whose parent is tourmaline, commonly green, blue or pink; the effect alone cannot establish the species or any treatment.
Evidence grade BScope: A name-level synthesis, not a specimen-level conclusion; species and treatment still require testing.
Sources GIA Tourmaline Description · G&G Summer 2025
Limits of this research
- Research status: Only partial material-specific findings found; gaps are stated as gaps
- Chatoyancy is an optical phenomenon and its name is not an independent species; the parent species still requires testing.
- The sources give no timescale for cat's-eye tourmaline.
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
- Tourmaline Cat’s-eye
GB/T 16552—2017 5.3.1 · GB/T 16553—2017 §5.1.10.3
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
Tourmaline Cat’s-eye's material identity has open questions that are not fully settled; this site lists it as "Tourmaline Cat’s-eye" pending further verification.
Evidence
- GB/T · 5.3.1
What this means for you
Before buying, check the recommended listing name "Tourmaline Cat’s-eye" and any disclosed treatments on this page, and ask the seller for a grading report if in doubt.
Known uncertainty
- This entry's exact material identity is not fully settled.
- See “Disclosure and cautions” above
- Last reviewed
- 2026-09-26
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
Tourmaline Cat’s-eye — 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
- treated
Source & check 2026-09-25
- Source
- Fact checked on
- 2026-09-25
Tourmaline Cat’s-eye — 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
Source & check 2026-09-25
- Source
- 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
The care conclusions for Tourmaline Cat’s-eye all come from CIBJO, and all state that they apply only to treated Tourmaline Cat’s-eye. CleaningTreated Tourmaline Cat’s-eye must not be cleaned ultrasonically. ChemicalsOn contact with acids, alkalis and common chemicals: dyeing, oiling, resin impregnation, waxing or plastic impregnation are all not permanent, and treated Tourmaline Cat’s-eye should be kept away from all solvents (including detergents of every kind), chemicals and heat.
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 |
Treatments and identification leads
Registered treatmentsThe treatments registered for Tourmaline Cat’s-eye are fissure filling with oil and fissure filling with resin. Stability and frequencyFissure filling with oil has the treatment state treated, an unstable effect and occasional market prevalence; fissure filling with resin likewise has the treatment state treated, an equally unstable effect and rare market prevalence. Values not givenThe identification leads and sources for both are entered as “—” in the register, meaning the cited source gives no value, not “none”.
This table scrolls sideways on narrow screens.
| Treatment | Market frequency (CIBJO) | Stability (CIBJO) | GB/T 16552 category | JJA/AGL listing | Identification leads |
|---|---|---|---|---|---|
| fissure filling with oilStatus: treated | occasionally | unstable | — | — | — |
| fissure filling with resinStatus: treated | rarely | unstable | — | — | — |
Where each treatment acts (schematics): Filled / Fracture-filled
“—” means the cited source gives no value for that item, not “none”. Source: CIBJO Gemstone Book 2022
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 namesTourmaline Cat’s-eye is a natural inorganic gem material and a mineral or gem variety. The GB/T 16552—2017 text does not list Tourmaline Cat’s-eye separately; the name is built by the GB/T 16552—2017 naming rules, with the basic name Tourmaline. The suggested listing name is Tourmaline Cat’s-eye. Names in four languagesThe four-language names are given in Simplified Chinese, Traditional Chinese, English (Tourmaline Cat’s-eye) and Japanese (a transliteration, pending check); the Japanese name is the entry's own, and the Japanese GSJ wording for it is not yet verified by this site. Trade and mineralogical namesThe mineralogical name is Tourmaline cat’s-eye, meaning tourmaline showing chatoyancy. Institution usageAmong authority wordings, the FTC source text has no wording for this name (checked); the wordings of GIA, CIBJO 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
- トルマリン・キャッツ・アイ（待核） (not yet checked for this body — the entry's own Japanese name is shown)
- Name built by the GB/T naming rules (not listed as such)
- 碧玺猫眼 (GB/T 16552—2017 §5.3.1; basic name 碧玺)
- Mineralogical name
- Tourmaline cat's-eye: tourmaline showing chatoyancy
Four-language names
- 简体中文
- 碧玺猫眼
- 繁體中文
- 碧璽貓眼
- English
- Tourmaline Cat’s-eye
- 日本語
- トルマリン・キャッツ・アイ（待核）
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
What it is and how it's identified
Among the registered material facts for Tourmaline Cat’s-eye, Mohs hardness, density, refractive index and birefringence are all taken for tourmaline (the whole mineral group), not measured on Tourmaline Cat’s-eye separately. Under GB/T 16553—2017, tourmaline (the whole mineral group) has a Mohs hardness of 7–8; density of 2.46–3.26 g/cm³, the cited clause giving 3.06 with a tolerance of +0.20/−0.60, from which the limits are derived; refractive index of 1.615–1.655, the cited clause giving 1.624–1.644 with a tolerance of +0.011/−0.009, from which the limits are derived; and birefringence of 0.018–0.04, where this site notes that the clause has further sub-grades and the overall value is used. The optical effect is the cat's-eye effect: the cited clause lists the cat's-eye effect among the special optical effects in the tourmaline section, and under GB/T 16552—2017 Tourmaline Cat’s-eye means tourmaline showing the cat's-eye effect. Fluorescence, UV-visible spectrum, infrared spectrum and magnification are given in the cited clauses for tourmaline (the whole mineral group); see the material facts of the Tourmaline entry.
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 Tourmaline Cat’s-eye 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 Tourmaline Cat’s-eye (how to read class-level values).
Durability
Tourmaline Cat’s-eye — 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 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
For Tourmaline Cat’s-eye, the stability of fissure filling with oil is “unstable”.
CIBJO Gemstone Book 2022
- Treatment state
- treated
- Treatment
- fissure filling with oil
- Qualification
This says how well the treatment holds up, not how durable Tourmaline Cat’s-eye itself is.
- General note
- no durability verdict here
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
For Tourmaline Cat’s-eye, the stability of fissure filling with resin is “unstable”.
CIBJO Gemstone Book 2022
- Treatment state
- treated
- Treatment
- fissure filling with resin
- Qualification
This says how well the treatment holds up, not how durable Tourmaline Cat’s-eye itself is.
- General note
- no durability verdict here
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
Physical properties
Tourmaline Cat’s-eye — 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 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Tourmaline Cat’s-eye — 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 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Tourmaline Cat’s-eye — 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 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.10 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Tourmaline Cat’s-eye — optical effect (chatoyancy): chatoyancy (cat’s-eye effect)
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- Qualification
The clause we cite lists the cat’s-eye effect among the special optical effects of tourmaline; under GB/T 16552 §5.3.1 this name means tourmaline that shows it.
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
- CIBJO definitions
- chatoyancy
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
How far testing can go
Tourmaline Cat’s-eye — 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 2026-09-26
- Source
- Fact checked on
- 2026-09-26
For Tourmaline Cat’s-eye in trade, the reported frequency of fissure filling with oil is “occasionally”.
CIBJO Gemstone Book 2022
- Treatment state
- treated
- Treatment
- fissure filling with oil
Source & check 2026-09-26
- Source
- Fact checked on
- 2026-09-26
For Tourmaline Cat’s-eye in trade, the reported frequency of fissure filling with resin is “rarely”.
CIBJO Gemstone Book 2022
- Treatment state
- treated
- Treatment
- fissure filling with resin
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.
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.
- AQSIQ / SAC (China). GB/T 16553—2017 Gems — Testing.
- eCFR (United States). 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 (Tourmaline Cat’s-eye) is marked.
- Tourmaline
Sub-entries (11)
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Tourmaline-supergroup minerals and gem varieties | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Tourmaline Cat’s-eye 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. The entry exists so that buyers and sellers can check naming, disclosure and material facts item by item.