3.1" Sphalerite and Chalcopyrite Association - Peru

Sphalerite is a part of the sulfide group and typically exhibits a grey/black appearance due to high concentrations of impurities. In its purest state, sphalerite's 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 since iron easily replaces zinc in the process of formation.

Chalcopyrite is a brass-yellow colored mineral and an important copper ore. When weathered, chalcopyrite loses its metallic luster, turning a gray-green color. When exposed to acids, the tarnish can develop a red, blue, or purple iridescence: this acid-treated material is often sold under the name peacock ore.