Stichtite: Gemstones Information
Stichtite is Mg6Cr2(CO3)(OH)164H2O and is dimorphous with barbertonite. It forms commonly matted lilac to rose-pink aggregates of fibres or plates in the trigonal system with a perfect cleavage in one direction and feeling greasy to the touch; hardness 1.5–2, SG 2.16–2.22. The RI for the ordinary and extraordinary rays is 1.545 and 1.518, uniaxial negative (may be anomalously biaxial) with birefringence 0.02. The absorption spectrum is characteristic of Cr with lines in the red. Stichtite occurs as an alteration product of chromite in serpentinite; fine material from the Adelaide Ag-Pb mine, Dundas, Tasmania, Australia, and from asbestos mines at Stolzburg, Barberton district, Transvaal, South Africa.