en Stichtite

Stichtite
Stichtite
	Stichtite on serpentine, Dundas, Tasmania
General
Category	Carbonate minerals
Formula; (repeating unit)	Mg6Cr2CO3(OH)16·4H2O
IMA symbol	Stt
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

Stichtite is a mineral, a carbonate of chromium and magnesium; formula Mg₆Cr₂C O₃(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]