Sphalerite

Chemical Formula : (Zn,Fe)S
Hardness : 3.5-4
Cleavage : Six; perfect
Luster : Resinous to adamantine to sub-metallic
Color : Yellow, brown, red, green, black; rarely white or pale gray
Streak : Brown to Light Yellow
Density : 4.096
Diagnostic Features and Trivia : When scratched, a fresh surface of sphalerite commonly releases
H₂S gas, and so smells like rotten eggs.
Crystal System and Habit : Isometric; tetrahedral
Twinning : Twin axis [111]
Polymorphs : None
Index of Refraction : 2.37-2.5