SPHALERITE
Sphalerite is a somewhat common zinc sulfide mineral (ZnS). It has a
metallic to submetallic to resinous to adamantine luster. Many metals can
substitute for the zinc, such as iron, cadmium, and manganese. Sphalerite
almost always has some iron in it, so a better chemical formula would be
(Zn,Fe)S. Sphalerite has a wide color range, depending principally on
iron content. Pure to almost pure sphalerite is whitish to
greenish. With increasing iron content, sphalerite becomes yellowish to
brownish to blackish. One variety of sphalerite has a strikingly intense
dark red color (ruby sphalerite). It's streak color also varies with iron
content from whitish to pale yellowish to brownish. Sphalerite is also
distinctive in being moderately heavy for its size and having six different
planes of cleavage.
Sphalerite is the most important zinc ore
mineral. Zinc produced from sphalerite is used for many purposes,
including mixing with copper to produce brass, rust protection of iron &
steel, and for making modern American pennies (although the cost of making each
zinc penny is >1¢).
Sphalerite cleavage fragment (3.7 cm across at its widest) from a mine in the
Tri-State Mining District, Ottawa County, Oklahoma, USA.
Sphalerite (field of view ~3 cm across)
Sphalerite (black) & barite (whitish-yellow) from the Cumberland Mine, Smith
County, Tennessee, USA (CMC RM 1140, Cincinnati Museum Center's rock &
mineral collection, Cincinnati, Ohio, USA).