Sphalerite,zinc sulfide,is the world's most important zinc ore. It occurs all over the world,generally associated with sulfides of lead (galena) and iron (pyrite). Occasionally sphalerite crystals,which are intrinsically colorless,are transparent and strongly colored by a varying content of iron. The resulting hues,in shades of green,yellow,orange and red,are saturated and striking. Sphalerite,although beautiful,is soft,fragile,difficult to cut,and unsuited for jewelry. Cutting material comes from Spain,Colorado and Mexico. The gems pictured range in size from about 2 to 15 carats,but orange stones over 100 carats have been produced |