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UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Mineral / gemstone variety · Natural identity; treatment status unknown
Quartz Cat’s-eye
Quartz showing the cat’s-eye effect. Under GB/T 16552 §5.3.1 it is named by adding "Cat’s-eye" after the basic name; "Cat’s-eye" alone refers only to chrysoberyl cat’s-eye. 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 Quartz 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 Quartz Cat’s-eyeIdentification points from the research literature; how far lab testing can go and whether a synthetic exists
- Caring for and wearing Quartz Cat’s-eyeDurability indicators and wearing advice
- Hardness, density and refractive index of Quartz Cat’s-eyeEach value with its source and check date
- Quartz 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?
- Name origin and history of Quartz Cat’s-eyeWhere the name comes from
- Listing and disclosing Quartz 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
Quartz cat's-eye is quartz that shows chatoyancy. The phenomenon comes from a set of parallel inclusions — tiny needles or channels. Where inclusions of that kind run parallel, scattering and reflection of light build a distinct band; cutting the stone as a cabochon makes a light band, aligned at right angles to the needle/channel axis, appear on the surface as a sharp line — the phenomenon called chatoyancy. When two or more such sets of parallel inclusions cross, the intersecting bands that result give asterism, and how many rays appear is fixed by how many bands cross. Its identity as a quartz gem variety stays SiO2 quartz; a cat's-eye is an optical phenomenon, not a separate mineral species.
Scope: Applies to the optical origin and identity definition of quartz cat's-eye; the specific locality requires separate evidence, and this record contains no identification conclusion for any particular sample.
Sources G&G Summer 2022 · Handbook of Mineralogy
Where it forms
Quartz hosts containing oriented needle/channel inclusions; cut as cabochons to display the effect
Sources G&G Summer 2022
How it forms, step by step
Quartz crystallizes from silica-bearing fluids and incorporates needle/channel inclusions, contemporaneously or later.
Sources G&G Summer 2022
These inclusions become arranged in a series of parallel, oriented sets within the material.
Sources G&G Summer 2022
When cut as a cabochon and correctly oriented, the light band perpendicular to the inclusion axis appears on the surface as a sharp chatoyant line.
Sources G&G Summer 2022
Link to appearance
A sharp light line (the cat's-eye) on the cabochon lies perpendicular to the inclusion direction; with several intersecting parallel sets, multiple bands and thus a star appear.
Sources G&G Summer 2022 · Handbook of Mineralogy
Timescale
The sources give no timescale for the formation of needle inclusions in quartz.
Sources G&G Summer 2022 · Handbook of Mineralogy
Related base materials
- Quartz (SiO2): variety-of | Quartz cat's-eye is quartz showing the cat's-eye effect (chatoyancy)
Causes of colour and optical effects
Chatoyancy is produced by a series of parallel inclusions of tiny needles or channels: light produces a band by scattering and reflection, appearing as a sharp line on a cabochon surface.
Evidence grade AScope: States the general cause of chatoyancy; not elaborated gem-by-gem beyond quartz.
Sources G&G Summer 2022
If several series of parallel inclusions intersect, multiple intersecting bands appear, producing asterism; the number of rays depends on the number of intersecting bands.
Evidence grade AScope: Relates asterism to the number of bands; quartz cat's-eye is typically a single line.
Sources G&G Summer 2022
Where the name comes from
The origin of the variety name "quartz cat's-eye" itself is not given in the cited sources. The etymology below belongs to the underlying mineral quartz: its name is of obscure origin in the Middle Ages, first applied to gangue in Saxony, Germany. This etymology belongs to the underlying mineral, not to the name "quartz cat's-eye" itself.
Evidence grade BScope: The etymology explains only the origin of the name; it does not establish the material's composition, locality, naturalness, or treatment.
Sources Handbook of Mineralogy
How it is identified
The colour and inclusion appearance of 'quartz-cats-eye' cannot establish whether a stone is natural, synthetic or treated: quartz varieties that look alike may differ entirely in composition, growth history and treatment, and synthetic and natural quartz share essentially the same composition and physical properties, so the unaided eye cannot separate them. Laboratory identification rests on measurable properties and the division of labour between instruments — a polariscope with a conoscope lens can judge colour-zoning orientation from extinction and optic-axis readings, a refractometer gives refractive-index values, and EDXRF with infrared spectroscopy supplies chemical and structural fingerprints. Limitations: some methods depend on how the stone was cut and on comparison with reference material, and the final conclusion must be issued by an accredited gemological laboratory through testing rather than inferred from appearance.
Evidence grade AScope: Identification and separation points; testing must be performed by an accredited gemological laboratory, and no self-test thresholds are given.
Sources G&G Summer 2014 · CIBJO Gemstone Book 2022
Other research findings
Quartz cat's-eye is quartz showing chatoyancy; its identity is SiO2 quartz, and the cat's-eye is an optical effect rather than an independent mineral species.
Evidence grade BScope: Defines the material identity of quartz cat's-eye; origin and quality excluded.
Sources Handbook of Mineralogy
Limits of this research
- Research status: Only partial material-specific findings found; gaps are stated as gaps
- The sources give no timescale or specific locality for the needle inclusions behind quartz cat's-eye.
- The specific variety and origin of quartz cat's-eye require separate evidence; no specimen identification is made here.
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
- Quartz Cat’s-eye
GB/T 16552—2017 5.3.1 · GB/T 16553—2017 §5.1.16.3
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
Quartz Cat’s-eye's material identity has open questions that are not fully settled; this site lists it as "Quartz Cat’s-eye" pending further verification.
Evidence
- GB/T · 5.3.1
What this means for you
Before buying, check the recommended listing name "Quartz 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
No care facts are recorded for this entry itself. Its parent material has care records: see Quartz.
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
tough when massive
Cleavage
Cleavage very rarely observable; poor on {1011}, {0111}, {1010} and others; rhombohedral parting
Daily wear
Hardness 7 resists scratching by ordinary metal and grit, and massive material has good toughness, so it is relatively durable for daily wear; however a hard impact can still chip it, and sudden temperature changes should be avoided to prevent cracking.
Care
Warm water with mild soap and a soft brush suffices; rinse and dry with a soft cloth. For dyed, resin-impregnated or fractured treated material, avoid ultrasonic/steam cleaning and acid washes, and avoid prolonged heat or sunlight.
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 material's general properties and is not a finished-product durability promise; it gives no warranty of any specific piece's durability or safety, and the durability of treated (filled, dyed, coated) or composite/assembled material must be assessed separately.
VerifyNames, standards, technical facts, clauses and sources
Names
Standard and listing namesQuartz Cat’s-eye is formed under the naming rules of GB/T 16552—2017, by adding “cat's-eye” to the basic name quartz; the original standard does not list the name separately. The suggested listing name is Quartz Cat’s-eye. The mineralogical description is quartz showing chatoyancy. Names in four languagesThe four-language names cover Simplified Chinese, Traditional Chinese, English (Quartz Cat's-eye) and Japanese (to be checked). Institution usageOn authority wording, the FTC text on file has no wording for this name (checked), and the wording of GIA, CIBJO and Gem-A is unchecked; bodies without a record show the entry's own English name, which does not represent their position. Japanese namesThe GSJ (Japan) formal name is recorded as still to be checked; the GSJ wording for this name is not yet verified by this site, and the entry's own Japanese name is shown.
- GSJ (Japan) formal name
- クォーツ・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)
- 石英猫眼 (GB/T 16552—2017 §5.3.1; basic name 石英)
- Mineralogical name
- Quartz cat's-eye: quartz showing chatoyancy
Four-language names
- 简体中文
- 石英猫眼
- 繁體中文
- 石英貓眼
- English
- Quartz Cat’s-eye
- 日本語
- クォーツ・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
- Quartz and chalcedony materials
- 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 material facts for Quartz Cat’s-eye, whole-class features such as chemical composition, fluorescence, UV-visible spectrum, infrared spectrum and magnification are written in the cited clause for rock crystal (the whole class) and are not repeated for Quartz Cat’s-eye; see the material facts on the Rock Crystal entry. As written for rock crystal (the whole class), Mohs hardness is 7; density is 2.64–2.69 g/cm³, the cited clause giving 2.66 with tolerance (+0.03/−0.02), from which the limits are derived; refractive index is 1.544–1.553; birefringence is 0.009. The optical effect recorded for Quartz Cat’s-eye is chatoyancy; the cited clause lists chatoyancy among the special optical effects in its rock crystal section; under the naming rules of GB/T 16552—2017, the name Quartz Cat’s-eye means quartz showing chatoyancy; and CIBJO glosses it as chatoyancy.
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, luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for rock crystal (the whole class), so they are not repeated on the Quartz Cat’s-eye page; see the material facts on the Rock Crystal entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Quartz Cat’s-eye (how to read class-level values).
Durability
Quartz Cat’s-eye — Mohs hardness: 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
- What this covers
- rock crystal (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.16 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Quartz Cat’s-eye — density: 2.64–2.69 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- rock crystal (the whole class)
- Qualification
The clause we cite gives 2.66, with a stated tolerance of +0.03 / -0.02. The range shown here is worked out from that.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.16 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Quartz Cat’s-eye — refractive index: 1.544–1.553
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- rock crystal (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.16 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Quartz Cat’s-eye — birefringence: 0.009
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- rock crystal (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.16 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Quartz 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 rock crystal; under GB/T 16552 §5.3.1 this name means quartz that shows it.
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.1.16 (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): 1.548 / 2.67; Closest values: 1Agate 1.537 / 2.63, 2Shoushan Stone 1.56 / 2.7, 3Changhua Stone 1.56 / 2.6, 4Bamboo Coral 1.57 / 2.65, 5Synthetic Beryl 1.57 / 2.69
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
In the registration of the CIBJO official Gemstone Book (2022), the entry on whether a synthetic is on the market states that no synthetic counterpart of Quartz Cat’s-eye is commercially available; this registration in the CIBJO official Gemstone Book (2022) applies to any treatment state.
How far testing can go
Quartz 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
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.
- RRUFF Project, in partnership with the IMA – International Mineralogical Association. IMA Mineral List.
- 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 Quartz on this site: 74 entries listed by this site's parent-entry links; synthetic, treated and similar entries carry their recorded state after the name; this page (Quartz Cat’s-eye) is marked.
- Quartz
Sub-entries (57)
- Agate
Sub-entries (1)
- Amethyst
- Ametrine
- Aventurine Quartz
- Aventurine Quartz / Green Aventurine
- Banded Agate
- Black Agate
- Bloodstone / Heliotrope
- Blue Lace Agate
- Carnelian
- Chalcedony
Sub-entries (2)
- Chrysoprase
- Citrine
- Clear Quartz / Rock Crystal
- Coated Quartz
- Colourless to White Quartz (brand name: Azeztulite)
- Crazy Lace Agate
- Dendritic Agate
- Dyed Agate (Treated: dyed)
- Elestial Quartz / Skeletal Quartz
- Eye Agate
- Flower Agate / Cherry Blossom Agate
- Green Quartz
- High-clarity quartz with golden needle-like inclusions
- Included Quartz
- Jasper
Sub-entries (1)
- Madeira Citrine
- Malachite Agate
- Morion / very dark Smoky Quartz
- Moss Agate
- Moss Chalcedony
- Multi-inclusion Quartz
- Onyx (banded chalcedony)
- Phantom Quartz
- Prase
- Prasiolite / Green Quartz
- Quartz Cat’s-eye
- Quartz claimed to be from the Himalayas
- Quartz Crystal
- Quartz with dark needle-like inclusions
- Quartz with fine fibrous inclusions
- Quartz with flower-like inclusions
- Quartz with golden needle-like inclusions
- Quartz with green needle-like inclusions
- Quartzite Jade
- Quartzose Jade
- Red Agate
- Rock Crystal
- Rose Quartz
- Rutilated Quartz
- Sard
- Sardonyx
- Silicified Asbestos
Sub-entries (2)
- Hawk’s Eye
- Tiger’s Eye
Sub-entries (1)
- Smoky Quartz
- Smoky Quartz (brown variety)
- Strawberry Quartz
- Yellow-green Quartz
- Agate
This table scrolls sideways on narrow screens.
| Page | Content | Status |
|---|---|---|
| Browsing family | Quartz and chalcedony materials | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Quartz 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.