Sphalerite is a rare collector’s gem whose claim to fame is exceptional dispersion or fire. In fact its dispersion rating is three times as high as that for diamond But sphalerite is a relatively soft gem, with a hardness of only 3.5 to 4 on the Mohs scale, about the same as fluorite.
Sphalerite is a zinc sulphide and is best known in the mineral world as the chief ore of zinc. Most sphalerite contains iron and when the iron content is high it is an opaque black. The rare gem-quality crystals have a very low iron content and considerable transparency. They are typically a yellowish to honey brown, red to orange, or green.
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