Stichtite

{{Short description|Hydrotalcite group mineral}} {{Infobox mineral |boxbgcolor=#d177df| name = Stichtite | boxtextcolor = #fff | image = Stichtite- Lizardite.jpg | alt = | caption = Stichtite on [[Serpentine group|serpentine]], Dundas, Tasmania | category = [[Carbonate mineral]]s | formula = Mg₆Cr₂CO₃(OH)₁₆·4H₂O | IMAsymbol = Stt<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | strunz = 5.DA.50 | dana = | system = [[Trigonal crystal system|Trigonal]] | class = Hexagonal scalenohedral ({{overline|3}}m) <br/>[[H-M symbol]]: ({{overline|3}} 2/m) | symmetry = ''R''{{overline|3}}m | unit cell = a = 6.19, c = 46.47&nbsp;[Å]; Z&nbsp;=&nbsp;3 | color = | colour = Lilac to rose-pink | habit = Fibrous to platy aggregates | twinning = | cleavage = Perfect on {0001} | fracture = | tenacity = flexible, not elastic | mohs = 1.5–2 | lustre = Waxy to resinous | streak = Very pale lilac to white | diaphaneity = Transparent | gravity = 2.16 | density = | polish = | opticalprop = Uniaxial (+) | refractive = n_ω = 1.516 n_ε = 1.542 | birefringence = δ = 0.026 | pleochroism = Weak; O = dark rose-pink to lilac E = light rose-pink to lilac | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = <ref name=HBM>[http://rruff.info/doclib/hom/stichtite.pdf Stichtite data in the Handbook of Mineralogy]</ref><ref name=Mindat>[http://www.mindat.org/min-3784.html Stichtite on Mindat.org]</ref><ref name=Webmin>[http://webmineral.com/data/Stichtite.shtml#.U590bfldXfI Stichtite data on Webmineral.com]</ref> }}

'''Stichtite''' is a mineral, a [[Carbonate mineral|carbonate]] of [[chromium]] and [[magnesium]]; formula Mg₆Cr₂[[carbon|C]][[oxygen|O]]₃(O[[hydrogen|H]])₁₆·4[[water|H₂O]]. Its colour ranges from pink through lilac to a rich purple colour. It is formed as an alteration product of [[chromite]]-containing [[Serpentine group|serpentine]]. It occurs in association with [[barbertonite]] (the [[Hexagonal crystal system|hexagonal]] [[Polymorphism (materials science)|polymorph]] of Mg₆Cr₂CO₃(OH)₁₆·4H₂O), chromite and [[antigorite]].<ref name=HBM/>

Discovered in 1910 on the west coast of [[Tasmania]], [[Australia]], it was first recognised by A.S. Wesley a former chief chemist with the [[Mount Lyell Mining and Railway Company]], it was named after [[Robert Carl Sticht]] the manager of the mine.<ref> Tasmania Department of Mines, Geological Survey Record Number 9 ''Catalogue of the Minerals of Tasmania''. Revised edition 1970, page 96 </ref>

It is observed in combination with green serpentine at Stichtite Hill near the Dundas Extended Mine, [[Dundas, Tasmania|Dundas]] – east of [[Zeehan, Tasmania|Zeehan]], as well as on the southern shore of [[Macquarie Harbour]]. It is exhibited in the West Coast Pioneers Museum in Zeehan. The only commercial mine for stichtite serpentine is located on Stichtite Hill{{cn|date=November 2014}}. Stichtite has also been reported from the [[Barberton District]], [[Transvaal Province|Transvaal]]; Darwendale, [[Zimbabwe]]; near [[Bou Azzer]], [[Morocco]]; [[Cunningsburgh]], the [[Shetland Islands]] of [[Scotland]]; [[Langban]], [[Varmland]], [[Sweden]]; the [[Altai Mountains]], [[Russia]]; [[Langmuir Township]], [[Ontario]] and the [[Megantic, Quebec]]; [[Bahia, Brazil]]; and the [[Keonjhar district]], [[Orissa, India]].<ref name=HBM/>

It is sometimes used as a gemstone.<ref>{{Cite web|url=https://www.gemdat.org/gem-3784.html|title=Stichtite gemstone information}}</ref>

<gallery widths="175px" heights="125px" > File:Stichtite on serpentine Basic hydrous magnesium chromate and carbonate New Amianthus Mine Transvaal South Africa 1623.jpg|Stichtite on serpentine, New Amianthus Mine, [[Transvaal Province|Transvaal]] South Africa </gallery>

==References== {{reflist}}

==External links== {{Commonscat}} * http://www.asap.unimelb.edu.au/bsparcs/biogs/P002619b.htm Sticht, Robert Carl – Bright Sparcs Biographical entry

[[Category:Magnesium minerals]] [[Category:Chromium minerals]] [[Category:Carbonate minerals]] [[Category:Hydroxide minerals]] [[Category:Tetrahydrate minerals]] [[Category:Western Tasmania]] [[Category:Trigonal minerals]] [[Category:Minerals in space group 166]] [[Category:Gemstones]] [[Category:Minerals described in 1910]]