Sphalerite
Sphalerite is a sulfide mineral with the chemical formula S. It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Valley type, and volcanogenic massive... Wikipedia
Formula: (Zn,Fe)S
Cleavage: perfect dodecahedral on
Color: Light to dark brown, red-brown, yellow, red, green, light blue, black and colourless
Crystal system: Cubic
Fracture: Uneven to conchoidal
Luster: Adamantine, resinous, greasy
Refractive index: nα = 2.369