Is tiger’s eye asbestos?
Tiger’s eye is quartz, hardness 7, tied to crocidolite, the blue asbestos UK law names. How its fibres sit is disputed. No safety verdict or advice is given.
Tiger’s eye is a quartz gem, hardness 7, whose shimmer Penn State geologists traced in 2003 to fibres of crocidolite, the blue asbestos named in regulation 2 of the UK Control of Asbestos Regulations 2012. An 1873 account had quartz replacing those fibres entirely. This page gives no safety verdict; that belongs with HSE and a clinician.
In short
- What the sources say tiger’s eye is. The International Gem Society quartz article lists tiger’s eye among the quartz varieties. The Penn State news release of 2 April 2003 says geologists since 1873 had taken it for quartz replacing crocidolite, “a blue form of asbestos”, and reports Heaney and Fisher’s finding (Geology, April 2003) that it is not a pseudomorph. Quartz, on its sheet, is hardness 7, density 2.65; see quartz.
- The two accounts disagree on where the crocidolite is. As Penn State summarises the old view, quartz replaced most of the crocidolite, and in tiger’s eye the pseudomorphism went to completion. Heaney and Fisher describe quartz and crocidolite growing together in repeatedly cracked and resealed veins, with the shimmer coming from crocidolite, not quartz. The Scientific American Rosetta Stones blog (29 July 2015) notes there is still some disagreement.
- What the regulation names. The Control of Asbestos Regulations 2012, regulation 2 reads: asbestos means the following fibrous silicates, and lists asbestos actinolite, asbestos grunerite (amosite), asbestos anthophyllite, chrysotile, crocidolite and asbestos tremolite, each with a CAS number. Crocidolite is item (e), CAS No 12001-28-4. Tiger’s eye and quartz are not named.
- The 5-of-6 name check. Strip the word asbestos and the bracketed trade name, and a script over the September 2026 IMA-CNMNC Master List finds rows for 5 of the 6 minerals in regulation 2: actinolite, grunerite, anthophyllite, chrysotile and tremolite. Crocidolite has no row. The Handbook riebeckite sheet records riebeckite in iron formations as asbestiform “crocidolite”.
- No verdict here. This page reports what the sources and the regulation state. It does not say tiger’s eye is or is not safe, and gives no handling, cutting, wearing or storage advice. Questions about exposure go to the HSE asbestos pages and a clinician. This is not health, safety or legal advice.
| Source (date) | What tiger’s eye is | Where the crocidolite is | What makes the shimmer | What makes the gold-brown colour |
|---|---|---|---|---|
| Wibel (1873), as summarised by Penn State and Science News, 2003 | Quartz pseudomorph after crocidolite | Replaced by quartz; in tiger’s eye the replacement went to completion | Originally attributed to chalcedony replacing fibrous crocidolite | Rusting of iron in the asbestos (Penn State); some iron in the bluish crocidolite turned to brownish iron oxide (Science News, describing Wibel) |
| Heaney and Fisher, Geology 31, 323 (April 2003), as reported by Penn State | Not a pseudomorph: formed by a discontinuous crack-seal mechanism | Grown with the quartz; fibres as inclusions within quartz columns (Scientific American blog, 2015) | Crocidolite, not quartz | Some of the iron in the crocidolite oxidizes |
| Science News (22 April 2003) | Quartz columns more than 100 micrometres across and up to 10 mm long | Parallel, needlelike crystals of iron-bearing asbestos called crocidolite | Reflection from the crocidolite fibres | — |
| Gutzmer, Beukes and Cairncross, Comment, Geology 32, e44–e45 (2004), with Reply | Bibliographic record only; content not read for this page | — | — | — |
| Control of Asbestos Regulations 2012, reg. 2 (revised text, read 14 October 2026) | Not named | Crocidolite named as asbestos, item (e), CAS No 12001-28-4 | — | — |
| IMA list, September 2026 (script) | No tiger’s eye row; quartz SiO2 is a row | No crocidolite row; riebeckite is a row, Rd, 2012 s.p., Yemen | — | — |
| Handbook riebeckite sheet | Not mentioned | Riebeckite in iron formations as asbestiform “crocidolite” | — | — |
Is tiger’s eye asbestos? What the sources and the law say
Tiger’s eye is a quartz gem material whose fibrous look the sources tie to crocidolite, and crocidolite is one of the six minerals UK law names as asbestos. The International Gem Society lists tiger’s eye among the quartz varieties. The Penn State release of 2 April 2003 calls crocidolite “a blue form of asbestos”; Science News calls it an often bluish, iron-bearing form of asbestos. Neither source gives a fibre content for tiger’s eye, and this page gives none.
What the regulation names. Regulation 2 of the Control of Asbestos Regulations 2012 reads, in its revised text on legislation.gov.uk, read on 14 October 2026: asbestos means the following fibrous silicates: (a) asbestos actinolite, CAS No 77536-66-4; (b) asbestos grunerite (amosite), CAS No 12172-73-5; (c) asbestos anthophyllite, CAS No 77536-67-5; (d) chrysotile, CAS No 12001-29-5 or CAS No 132207-32-0; (e) crocidolite, CAS No 12001-28-4; and (f) asbestos tremolite, CAS No 77536-68-6. The regulation names minerals. It does not name tiger’s eye, and this page does not interpret how the definition applies to a stone that contains a named mineral inside quartz.
The same regulation, other minerals. The live pages is actinolite asbestos and is scolecite asbestos read regulation 2 against actinolite and against a fibrous zeolite; their analyses are linked rather than repeated.
Is tiger’s eye a pseudomorph? Two accounts, 130 years apart
Whether quartz replaced the crocidolite in tiger’s eye, or grew alongside it, has been disputed since 2003. Penn State’s release says that since 1873 geologists had believed tiger’s eye to be an example of pseudomorphism, after Wibel: quartz replacing crocidolite, with the remaining asbestos giving hawk’s eye its bluish colour, and in tiger’s eye the pseudomorphism going to completion, the rusting of iron in the asbestos giving the gold.
The 2003 account. Peter Heaney and Donald Fisher, in Geology for April 2003 (vol. 31, p. 323), examined tiger’s eye by light microscopy, X-ray diffraction and transmission electron microscopy. Penn State quotes Heaney: no chalcedony is present in the South African specimens examined, and the fabrics are quite consistent with formation by a discontinuous crack-seal mechanism. Science News reports column-shaped quartz crystals more than 100 micrometres across and up to 10 mm long, a crystal form so uniform that, it says, pseudomorphism does not produce it. In their account crocidolite, and not quartz, causes the shimmer, and the gold-brown comes after some of the iron in the crocidolite oxidizes.
Not settled. A Comment by Gutzmer, Beukes and Cairncross and a Reply by Heaney and Fisher were published in Geology 32 (2004), e44–e45; its content was not read for this page and is not characterised here. The Scientific American Rosetta Stones blog (29 July 2015) says there is still some disagreement over whether Heaney and Fisher were right. Penn State dates large South African sources of the stone to the 1880s.
Is crocidolite a mineral? The 5-of-6 name check
Crocidolite is the Handbook’s name for asbestiform riebeckite, and of the six names in regulation 2, read as mineral names, it is the one with no row of its own on the IMA list. Method: each of the six names in regulation 2 was reduced to its mineral name, dropping the word asbestos and the bracketed trade name amosite, and searched as a row name in the September 2026 IMA list (pdftotext -layout; a row is a line whose first word is the name). Five are rows: actinolite, grunerite, anthophyllite and tremolite, each redefined in 2012, and chrysotile, Mg3Si2O5(OH)4, redefined in 2007. Crocidolite and amosite have no row; nor does tiger’s eye.
Where crocidolite sits. The Handbook riebeckite sheet gives riebeckite as an alkali amphibole, commonly fibrous, asbestiform, with hardness 6 and density 3.28 to 3.44, and its Occurrence line reads: in iron formations as asbestiform “crocidolite”. Its Distribution field names South Africa, north from Koegas, Cape Province, and east of Pietersburg, Transvaal, and Wittenoom and elsewhere in the Hamersley Ranges, Western Australia. The IMA list gives riebeckite as ☐Na2(Fe2+3Fe3+2)Si8O22(OH)2, Rd, 2012 s.p., Yemen.
Why the name check matters to a label. A label reading crocidolite records the regulation’s word and a habit, not an IMA species; the species is riebeckite. A label reading tiger’s eye records a gem name; the species, per the IGS, is quartz. Neither label says how much crocidolite a piece contains.
Is tiger’s eye safe? Who answers that, and what this page does not say
This page does not say whether tiger’s eye is safe or dangerous, to wear, handle, cut or keep. It reports what the regulation names, what the formation studies describe and what the sheets record. Not one of those sources assesses the exposure from a polished stone, and a mineral being named in a regulation is not by itself an exposure finding either way.
Where the answers are. The HSE asbestos pages cover the law, the duties and licensed work under the Control of Asbestos Regulations 2012. A concern about your own exposure belongs with a clinician. The site’s general page is toxic minerals in a collection. This is not health, safety or legal advice, and no handling advice is given here, deliberately.
When the answer changes. On the 1873 account, the crocidolite in tiger’s eye is replaced; on the 2003 account, it is still there as fibres in the quartz; the Scientific American blog says hawk’s eye has more unweathered crocidolite. Any of those may matter to the people named above, and none is decided here. The safety and identification guides are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.