Stichtite

Stichtite

Stichtite on serpentine, Dundas, Tasmania
General
Category Carbonate minerals
Formula
(repeating unit)		 Mg6Cr2CO3(OH)16·4H2O
Strunz classification 5.DA.50
Crystal system Trigonal
Crystal class Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space group R3m
Unit cell a = 6.19, c = 46.47 [Å]; Z = 3
Identification
Colour Lilac to rose-pink
Crystal habit Fibrous to platy aggregates
Cleavage Perfect on {0001}
Tenacity flexible, not elastic
Mohs scale hardness 1.5 - 2
Lustre Waxy to resinous
Streak Very pale lilac to white
Diaphaneity Transparent
Specific gravity 2.16
Optical properties Uniaxial (+)
Refractive index nω = 1.516 nε = 1.542
Birefringence δ = 0.026
Pleochroism Weak; O = dark rose-pink to lilac E = light rose-pink to lilac
References [1][2][3]

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.[1]

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.[4]

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.[1]

References

  1. 1 2 3 Stichtite data in the Handbook of Mineralogy
  2. ↑ Stichtite on Mindat.org
  3. ↑ Stichtite data on Webmineral.com
  4. ↑ Tasmania Department of Mines, Geological Survey Record Number 9 Catalogue of the Minerals of Tasmania. Revised edition 1970, page 96
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