Yellow resinous crystal aggregates of the very rare tin sulphide berndtite (labeled as berndtite-3R in the plastic box) in a whitish matrix. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Berndtite
The rare natural form of tin(IV) sulfide — a brown, water-insoluble semiconductor.
Intro adapted from Wikipedia (CC BY-SA).
Berndtite is an IMA-recognized mineral species in the sulfide class, with the chemical formula SnS₂.
It crystallizes in the hexagonal crystal system (space group P-3m1). It is a member of the Melonite structural group.
Key properties: specific gravity 4.5; Golden yellow streak; Resinous. Streak: Golden yellow luster.
IMA symbol Bti, IMA status: approved, named in 1966.
Found as a secondary mineral in tin sulfide ores (Cerro de Potosı́, Bolivia); a secondary mineral in a tin-bearing pegmatite (Lagares-do-Estanho tin pegmatite); in a high-temperature deposit, hydrothermally altered (Arandis, Namibia).
It is found associated with Stannite, pyrite, cassiterite, sulfur.
The name refers to Dr. Fritz Berndt, German mineralogist, Corporatión Minera de Bolivia, Oruro, Bolivia.