Sphalerite

Physical Properties
Chemical formula	ZnS
Class	Sulfide
Crystal system	Cubic
Habit	Combinations of tetrahedra, dodecahedra, and cubes Commonly forms cleavable masses
Color	Brown-orange-red Colorless when pure Brown Black Yellow
Hardness	3.5 to 4
Specific gravity	4.0
Cleavage	Perfect dodecahedral {110}
Fracture	Conchoidal
Luster	Adamantine Resinous
Transparency	Transparent to opaque
Streak	White to brown or yellow
Optical Properties
PPL	Colorless to pale brown or yellow Extremely high relief Good cleavage
XPL	Isotropic
δ	None
Twinning	Polysnthetic twins are common
Special properties	May have faint garlic or sulfur smell, especially if powdered
	after Perkins, 355-356

Sphalerite in Hand Sample