Most often sphalerite is reddish-brown, but it can range from black to (in rare cases) clear. Dark specimens can appear somewhat metallic in luster, but otherwise its luster can be described as resinous or adamantine. Its Mohs hardness is 3.5 to 4. It commonly occurs as tetrahedral crystals or cubes as well as in granular or massive form.
Sphalerite can be found in many ore veins of sulfide minerals, commonly associated with galena and pyrite. Miners call sphalerite "jack," "blackjack," or "zinc blende." Its impurities of gallium, indium and cadmium make sphalerite a major ore of those metals.
Sphalerite has some interesting properties. It has excellent dodecahedral cleavage, which means that with careful hammer work you can chip it into nice 12-sided pieces. Some specimens fluoresce with an orange hue in ultraviolet light; these also display triboluminescence, emitting orange flashes when stroked with a knife.