2.8" Sphalerite, Marcasite & Barite On Dolomite - Missouri
This is an association of Sphalerite, marcasite and barite on a dolomite matrix from the Washington County Aggregates Quarry in Missouri.
Sphalerite is a part of the sulfides group and typically exhibits a grey/black appearance due to high concentrations of impurities. When sphalerite is in it's purest state, the chemical composition is ZnS, and can display a gemmy transparent light tan/yellow color. This is one of the few minerals that can form crystals ranging anywhere between gemmy and transparent to opaque and metallic-like. Opaque or cloudy sphalerite tends to be most abundant, due to the ease of iron replacing zinc in the process of formation.