Sharp yellow crystals of rosickyite on matrix from an unspecified off shore drill hole in the Pacific Ocean near California (Ventura County, California, United States of America). Rosickyite is a dimorphous with both, sulphur (α-sulphur) and β-sulphur. — Photo: David Hospital · CC BY-SA 4.0
Rosickýite
The monoclinic high-density polymorph of sulfur — soft pale-yellow crystals.
Intro adapted from Wikipedia (CC BY-SA).
Rosickýite is an IMA-recognized mineral species in the native element class, with the chemical formula S.
It crystallizes in the monoclinic crystal system (space group P2/c).
Key properties: Adamantine luster; optically biaxial.
IMA symbol Rký, grandfathered status — known before the IMA’s founding, named in 1931.
Found in hollow “limonite” nodules in a thin clay stratum (Havı́rna, Czech Republic); in fumaroles (Vulcano, Italy); an alteration product of pyrite-rich asphalt (La Presta mine, Switzerland).
It is found associated with Pyrite, gypsum, rozenite, sulfur, calcite, “limonite”, asphalt (La Presta mine, Switzerland).
The mineral was named to honor Professor Vojtěch Rosický (1880–1942), former Director of the Mineralogical and Petrological Institute of Masaryk University, Brno, Czech Republic.