Stichtite

Hydrotalcite group mineral
(repeating unit)Mg6Cr2CO3(OH)16·4H2OIMA symbolStt[1]Strunz classification5.DA.50Crystal systemTrigonalCrystal classHexagonal scalenohedral (3m)
H-M symbol: (3 2/m)Space groupR3mUnit cella = 6.19, c = 46.47 [Å]; Z = 3IdentificationColourLilac to rose-pinkCrystal habitFibrous to platy aggregatesCleavagePerfect on {0001}Tenacityflexible, not elasticMohs scale hardness1.5–2LustreWaxy to resinousStreakVery pale lilac to whiteDiaphaneityTransparentSpecific gravity2.16Optical propertiesUniaxial (+)Refractive indexnω = 1.516 nε = 1.542Birefringenceδ = 0.026PleochroismWeak; O = dark rose-pink to lilac E = light rose-pink to lilacReferences[2][3][4]

Stichtite is a mineral, a carbonate of chromium and magnesium; formula Mg6Cr2CO3(OH)16·4H2O. Its colour ranges from pink through lilac to a rich purple colour. It is formed as an alteration product of chromite containing serpentine. It occurs in association with barbertonite (the hexagonal polymorph of Mg6Cr2CO3(OH)16·4H2O), chromite and antigorite.[2]

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.[5]

It is observed in combination with green serpentine at Stichtite Hill near the Dundas Extended Mine, Dundas – east of 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[citation needed]. Stichtite has also been reported from the Barberton District, 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.[2]

It is sometimes used as a gemstone.[6]

  • Stichtite on serpentine, New Amianthus Mine, Transvaal South Africa
    Stichtite on serpentine, New Amianthus Mine, Transvaal South Africa

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c Stichtite data in the Handbook of Mineralogy
  3. ^ Stichtite on Mindat.org
  4. ^ Stichtite data on Webmineral.com
  5. ^ Tasmania Department of Mines, Geological Survey Record Number 9 Catalogue of the Minerals of Tasmania. Revised edition 1970, page 96
  6. ^ "Stichtite gemstone information".

External links

Wikimedia Commons has media related to Stichtite.
  • http://www.asap.unimelb.edu.au/bsparcs/biogs/P002619b.htm Sticht, Robert Carl – Bright Sparcs Biographical entry