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Stichtite

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Hydrotalcite group mineral
Stichtite
Stichtite on serpentine, Dundas, Tasmania
General
CategoryCarbonate minerals
Formula
(repeating unit)		Mg6Cr2CO3(OH)16·4H2O
IMA symbolStt
Strunz classification5.DA.50
Crystal systemTrigonal
Crystal classHexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space groupR3m
Unit cella = 6.19, c = 46.47 ; Z = 3
Identification
ColourLilac to rose-pink
Crystal habitFibrous to platy aggregates
CleavagePerfect on {0001}
Tenacityflexible, not elastic
Mohs scale hardness1.5–2
LustreWaxy to resinous
StreakVery pale lilac to white
DiaphaneityTransparent
Specific gravity2.16
Optical propertiesUniaxial (+)
Refractive indexnω = 1.516 nε = 1.542
Birefringenceδ = 0.026
PleochroismWeak; O = dark rose-pink to lilac E = light rose-pink to lilac
References

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.

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.

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. 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.

It is sometimes used as a gemstone.

  • 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. ^ 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

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