Stichtite and lizardite Locality: Stichtite Hill, Dundas mineral field, Zeehan District, Tasmania, Australia Size :15 × 14 cm. — Photo: Didier Descouens · CC BY 3.0
Stichtite
A lilac-to-purple magnesium-chromium carbonate formed where chromite-bearing serpentinite alters — Tasmania's mineral emblem.
Intro adapted from Wikipedia (CC BY-SA).
Stichtite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Mg₆Cr₂(CO₃)(OH)₁₆·4H₂O.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Hydrotalcite structural group.
Key properties: Mohs hardness 1.5–2; specific gravity 2.16; Very pale lilac to white streak; Waxy to resinous, somewhat pearly luster; refractive index 1.529; optically uniaxial.
IMA symbol Stt, IMA status: approved, named in 1910.
An alteration product of chromite in serpentinite.
It is found associated with Barbertonite, chromite, antigorite.
The mineral was named to honor Robert C. Sticht (1857–1922), formerly General Manager of the Mount Lyell Mining and Railway Company, Tasmania, Australia.