Extremely rare bright green xanthiosite on darker green aerugite, and associated to bunsenite, from the type locality for the three species (Johanngeorgenstadt, Erzgebirge, Saxony, Germany), and only one of the two known localities worldwide for aerugite. Three Ni mineral species and three TL in a single specimen. — Photo: David Hospital · CC BY-SA 4.0
Xanthiosite
A golden-yellow nickel arsenate first found in Germany in 1858.
Intro adapted from Wikipedia (CC BY-SA).
Xanthiosite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Ni₃(AsO₄)₂.
It crystallizes in the monoclinic crystal system (space group P2_1/c). It is a member of the Olivine-Sarcopside structural group.
Key properties: Mohs hardness 4; specific gravity 4.98–5.42.
IMA symbol Xth, IMA status: approved, named in 1965.
Found as a rare secondary mineral in hydrothermal Ni–As–U ore deposits.
It is found associated with Bismuth, bunsenite, aerugite (Johanngeorgenstadt, Germany); aerugite (South Terras mine, Cornwall, England).
Its name comes from the Greek for yellow and sulfur, in allusion to its distinctive sulfur-yellow color.