Mica is not just one mineral but is the name given to a group of similar
minerals. The mica minerals are easy to recognize. Because they have
perfect cleavage in one direction, they split into thin, flat sheets.
You can see through some mica sheets, and they are elastic enough to be
bent back and forth. (Another mineral, selenite gypsum, also will split
into thin, flat, transparent sheets, but selenite sheets break when you
bend them.)
[Illustration: Mica minerals have perfect cleavage in one direction,
resulting in thin, sheet-like cleavage fragments.]