Schists are usually differentiated from other foliated rocks on the basis of their crystal size, exhibiting crystals that are distinctly larger than those of slates and considerably smaller than gneisses. Schists are often distinguished from one another, however, based upon the dominant flaky minerals they contain. Some of the more common varieties are mica schist, talc schist, and hornblende schist. These and other schists are particular prevalent among the Precambrian rocks.