On this page
UnderstandWhat it is, what people ask, how far this page goes
Natural inorganic gem materials · Trade name: colour / appearance variety · Natural identity; treatment status unknown
Hawk’s Eye
Also known asBlue tiger eye · Eagle's Eye Stone (conditional name) · Falcon’s-eye
Silicified asbestos dominated by blue tones such as grey-blue or green-blue; GB/T 34098-2017 clause 5.5 permits the name “hawk’s eye”, but the basic name remains silicified asbestos. Also known as Blue tiger eye, Falcon’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 Hawk’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 Hawk’s EyeHow far lab testing can go
- Treatments and enhancements of Hawk’s EyeThe enhancements and treatments the GB/T and JJA/AGL tables list
- Hardness, density and refractive index of Hawk’s EyeEach value with its source and check date
- Hawk’s Eye 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 Hawk’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
Hawk's-eye (also falcon's-eye) appears in the authority text only as the 'less common dark blue variety' of tiger's-eye: it differs in that its amphibole needle inclusions are less altered (weathered) and thus retain the amphibole's original color, instead of weathering to iron oxides and turning golden-brown as in tiger's-eye. The source gives no hawk's-eye-specific account of its formation or its chatoyancy mechanism; these can only be inferred from the tiger's-eye section — namely the same chatoyant quartz (fibrous amphibole inclusions plus quartz) formed by pseudomorphism or crack-seal, with the cat's-eye effect from selective reflection off aligned fibrous inclusions. This inference is a cross-record extrapolation and must be explicitly flagged.
Scope: Applies only to the cat's-eye quartz described in the literature as the dark blue variety of tiger's eye, coloured by less-altered amphibole needles; does not cover other materials called hawk's-eye by dealers.
Sources G&G Summer 2025
Where it forms
The same iron-rich siliceous amphibole–quartz setting as tiger's-eye (inferred by extrapolation from the tiger's-eye record)
Sources G&G Summer 2025
A setting with less alteration, allowing the amphibole needles to retain their original color
Sources G&G Summer 2025
How it forms, step by step
(Inferred) fibrous crocidolite (riebeckite) forms in an iron-rich siliceous setting.
(Inferred) quartz associates with riebeckite by pseudomorphism or crack-seal, forming chatoyant quartz.
Unlike tiger's-eye, the amphibole needles are less altered (weathered), so they do not convert extensively to iron oxides and retain the amphibole's original (dark blue / blue-gray) color.
(Inferred) light reflects selectively off the aligned fibrous inclusions, producing the cat's-eye effect.
Link to appearance
The blue-gray/dark blue color comes from less-altered amphibole needles that retain their original color; the cat's-eye band direction is set by the fibrous inclusion orientation.
Sources G&G Summer 2025
Timescale
The source provides no formation timescale specific to hawk's-eye.
Sources G&G Summer 2025
Related base materials
- Tiger's-eye: Hawk's eye is the dark blue variety of tiger's eye
- Crocidolite (riebeckite): Fibrous sodic amphibole needles that retain their original colour
Supporting findings
Hawk's-eye's formation (pseudomorphism or crack-seal, quartz + riebeckite) is extrapolated from the tiger's-eye record; the authority text gives no hawk's-eye-specific genetic account.
Evidence grade CScope: An inference, to be treated as unsettled together with the tiger's-eye hypotheses.
Recorded localities
Authoritative sources list the localities below; the list is not exhaustive.
Africa
- Griqualand West, Northern Cape, South AfricaMindat's definition states the material comes from Griqualand
Sources Mindat: Hawk's Eye
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
Hawk's-eye's dark blue color arises because its amphibole needles are less altered and retain the amphibole's original color, rather than weathering to iron oxides.
Evidence grade AScope: A direct statement in the source on its color; the degree of alteration is not quantified.
Hawk's-eye's chatoyancy is produced by selective reflection off aligned fibrous inclusions — an inference extrapolated from the tiger's-eye section; the source has no hawk's-eye-specific account.
Evidence grade CScope: A cross-record extrapolation, not a direct statement about hawk's-eye in the source.
Other research findings
Hawk's-eye is the less common dark blue variety of tiger's-eye, also known as falcon's-eye.
Evidence grade AScope: The source mentions it in a single sentence with no independent definition or locality.
Limits of this research
- Research status: Formation, occurrence or other material-specific findings found in authoritative sources
- The authority text gives only a single sentence on hawk's-eye (a dark blue variety of tiger's-eye with less-altered amphibole needles) and no hawk's-eye-specific formation or light-mechanism account.
- The optical effect and formation mechanisms described here are extrapolated from tiger's-eye, so they rest on evidence level C only, as the scope of each conclusion states.
- Hawk's-eye is a commercial name, not a mineral species; same-named commercial material may vary in composition.
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
- Hawk's Eye
GB/T 34098—2017 §5.5, Table A.1, §6 b) · CIBJO Gemmological Laboratories Book 2024 §7.2.1.240 “Tiger’s-eye”
Construction or treatment status
Natural identity; treatment status unknown
Treatments recorded for this material: Dyed (via parent material), Filled / Fracture-filled (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
"Hawk’s Eye" is a market name rather than a mineral species name; before using it, verify: Industry-wide term that does not denote a single species.
What this means for you
Before buying, check the recommended listing name "Hawk'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
- 2026-09-01
Trade-name ruling
- Industry-wide term that does not denote a single species.
- Suggested listing name
- Hawk's Eye
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 |
|---|---|---|---|---|---|
| Dyeing | — | — | Treatment | — | — |
| Filling | — | — | Graded — see §5.4.1, Table 1 | — | — |
“—” means the cited source gives no value for that item, not “none”. Source: GB/T 16552—2017 Table B.1 (row for Silicified Jade)
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
Besides Hawk’s Eye, the name register records "Blue tiger eye", "Eagle's Eye Stone" and "Falcon’s-eye", for which no restriction on use as a name is recorded (GB/T 16552 revision draft for comment (2023, not in force) Table A.2; GB/T 16552—2017 no occurrence of “Eagle's Eye Stone” in the full text; CIBJO Gemstone Book 2022 Annex 8 “Falcon’s-eye, or Hawk’s-eye”); 2 further names in non-Latin scripts are listed in the name register below (2 with no restriction recorded on use as a name).
Trade and mineralogical namesHawk’s Eye is a trade name listed in the national standard, whose basic name is the GB/T basic name silicified asbestos; under the trade-name column of GB/T 34098—2017 Table A.1 (in the row for that basic name) it is listed as a trade name of that material, and trade names listed in the national standard are not used on their own. Recommended listing nameThe suggested listing name is Hawk’s Eye. Trade and mineralogical namesCommon market names include blue tiger's eye, hawk-eye stone, Blue tiger eye and Falcon’s-eye. Candidate search termsEagle's Eye Stone serves only as a search candidate, based on the draft for comment of the GB/T 16552 revision (2023, not in force), and the full text of GB/T 16552—2017 does not contain this name. Names in four languagesNames are given in four languages: Simplified Chinese, Traditional Chinese, English (Hawk’s Eye) and Japanese (a katakana transliteration); Japan's GSJ formal name is unchecked, and the entry's own Japanese name is shown. Institution usageOn authority wording, CIBJO records Falcon’s-eye, or Hawk’s-eye; the FTC text on file has no wording for this name (checked); GIA and Gem-A are unchecked, and where unchecked the entry's own English name is shown, which does not represent their position. Trade and mineralogical namesThe mineralogical name is registered as a bluish-grey chatoyant quartz pseudomorph material.
Name register
Every name recorded for this entry, with how it is classified, whether it may be matched to this entry automatically, whether it may be used as a product name, and the clause it rests on.
This table scrolls sideways on narrow screens.
| Name | Type | Matching | Use as a name | Basis |
|---|---|---|---|---|
| no restriction recorded (5) | ||||
| Blue tiger eyeEnglish | market name | matched automatically | no restriction recorded | editorial ruling (no clause cited) |
| Eagle's Eye StoneEnglish | synonym | search candidate only | no restriction recorded | GB/T 16552 revision draft for comment (2023, not in force) Table A.2; GB/T 16552—2017 no occurrence of “Eagle's Eye Stone” in the full text; Note: Draft standard for comment, not in force. |
| Falcon’s-eyeEnglish | market name | matched automatically | no restriction recorded | CIBJO Gemstone Book 2022 Annex 8 “Falcon’s-eye, or Hawk’s-eye” |
| 蓝虎眼石Simplified Chinese | market name | matched automatically | no restriction recorded | editorial ruling (no clause cited) |
| 鹰眼石Simplified Chinese | market name | matched automatically | no restriction recorded | editorial ruling (no clause cited) |
How each authority words this name: see Names › Authority wording.
- GSJ (Japan) formal name
- ホークスアイ (not yet checked for this body — the entry's own Japanese name is shown)
- Trade name listed in the GB/T standard (not used on its own)
- 鹰睛石 (GB/T 34098—2017 §5.5; basic name 木变石)
- Mineralogical name
- Blue-gray chatoyant quartz pseudomorph material
- Trade names and synonyms
- Blue tiger eye (market name) · Falcon’s-eye (market name) · Eagle's Eye Stone (synonym; conditional name)
Four-language names
- 简体中文
- 鹰睛石
- 繁體中文
- 鷹睛石
- English
- Hawk’s Eye
- 日本語
- ホークスアイ
GB/T 34098 trade names
- Position in Table A.1
- A trade name on the silicified asbestos row (under silicified jade); clause 5.5 says the same for blue-toned material
- How to name it
- Silicified asbestos, with the note “trade name: 鹰睛石 Yingjing Shi”
The full table and naming rule are on the Quartzose Jade page.
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
- Trade name: colour / appearance variety
- Mineral chemical class
- Silicates
- Construction or treatment status
- Natural identity; treatment status unknown
Treatments listed by standards
For GB/T 16552—2017 Annex B, Table B.1, this site applies the “Silicified jade (silicified asbestos/petrified wood/silicified coral)” row to Hawk’s Eye; Table B.1 lists silicified jade. On that basis, dyeing is listed as treatment, and the category of filling is defined by grade; the notes to Table B.1 and the definition of each grade are on this site's Gem treatments page, and the full row, with the effect column, is on the silicified jade page.
GB/T 16552-2017, Annex B, Table B.1
Under the “Silicified Jade (Silicified Asbestos/Silicified Wood/Silicified Coral)” row of Table B.1: Dyeing Treatment; Filling Graded — see §5.4.1, Table 1. The full row, with the effect column, is on the Silicified Jade 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
The material facts for Hawk’s Eye are registered for silicified jade (including silicified asbestos, petrified wood and silicified coral) as a whole class, not measured on Hawk’s Eye alone; for the silicified jade class, structure crystalline aggregate, Mohs hardness 5–7, cleavage none, density 2.48–2.85 g/cm³, optical character anisotropic aggregate, and birefringence not measurable on an aggregate. The refractive index of 1.544–1.553 is likewise given for the silicified jade class; the clause has finer sub-ranges and the value is registered as the overall value, as a site note. For the silicified jade class, the cat's-eye effect can occur; untreated, pleochroism is not measurable on an aggregate, the lustre is vitreous, greasy or waxy on fracture surfaces, and silicified asbestos may also show silky lustre. Chemical composition, luminescence, UV-visible spectrum, infrared spectrum and magnification are likewise written for the silicified jade class in the cited clause; they are not repeated among the Hawk’s Eye material facts, see the material facts on the Silicified Jade 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”.
Chemical composition, luminescence, UV-visible spectrum, infrared spectrum, magnification: these whole-class features are given in the cited clause for silicified jade (the whole class), so they are not repeated on the Hawk’s Eye page; see the material facts on the Silicified Jade entry.
Items below that name the class they cover give the cited clause’s value for that whole class, not a measurement of Hawk’s Eye (how to read class-level values).
Structure
Hawk’s Eye — structure (overall): crystalline aggregate
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Durability
Hawk’s Eye — Mohs hardness: 5–7
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
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hawk’s Eye — cleavage: none
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Physical properties
Hawk’s Eye — density: 2.48–2.85 g/cm³
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Optical
Hawk’s Eye — optic character: anisotropic aggregate
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hawk’s Eye — refractive index: 1.544–1.553
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
- General note
- the clause has finer ranges
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hawk’s Eye — birefringence: not measurable on an aggregate
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hawk’s Eye — pleochroism: not measurable on an aggregate
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
Hawk’s Eye — optical effect (chatoyancy): seen
GB/T 16553—2017
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (locator checked 2026-09-26)
- Fact checked on
- 2026-09-26
- CIBJO definitions
- chatoyancy
Quality factors
Hawk’s Eye — quality factor (lustre): vitreous; greasy or waxy on the fracture; silicified asbestos may also show a silky luster.
GB/T 16553—2017
- Treatment state
- untreated
- Does this standard apply
- applies to this entry
- What this covers
- silicified jade (the whole class)
Source & check 2026-09-26
- Source
- GB/T 16553—2017 Gems — Testing (GB/T): §5.2.6 (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): 1.548 / 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
The CIBJO laboratory protocol covers Hawk’s Eye under “Quartz” (§6.1.65): see identification on the Quartz entry; the required tests are listed on the CIBJO laboratory protocol table for Quartz.
How far testing can go
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 34098—2017 Quartzose jade — Classification and nomenclature.
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 (Hawk’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 |
| Treatments recorded for this material | Dyed (via parent material), Filled / Fracture-filled (via parent material) | Live |
| Related articles | To be added (placeholder) | Planned |
Who maintains this page
The material facts in the Hawk’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.