sulfur, graphite (the "lead" in pencils), gypsum, halite (rock salt),
borax, talc, asbestos and quartz. Undoubtedly, you'll have some
nonmetallic minerals in your collection. Rocks containing asbestos
are especially handsome and varied.

3. ROCK-FORMING MINERALS. These are the building materials of the
earth. They make mountains and valleys. They furnish the ingredients
of soil and the salt of the sea. They are largely silicates--that is,
they contain silicon and oxygen. (Silicon is a nonmetallic element,
always found in combination with something else. It is second only
to oxygen as the chief elementary constituent of the earth's crust.)

Other rock-forming minerals are the large family of micas, with names
like muscovite and phlogopite. There are the feldspars, including
albite and orthoclase. Others are amphiboles, pyroxenes, zeolites,
garnets and many others you may never find or hear about unless
you become a true mineralogist.

A rock may be made almost entirely of one mineral or of more than
one mineral. Rocks containing different combinations of the same
minerals are different. Even two things made of the same single
mineral can be quite different. Carbon may turn up as a lump of
coal or a diamond.


How Minerals Got Their Names

Names of most minerals end in "ite"--apatite, calcite, dolomite,
fluorite. But many do not: amphibole, copper (the most common pure
metal in rocks), feldspar, galena, gypsum, hornblende, mica, quartz.