Biotite and Muscovite are members of the Mica Group of silicates. The two minerals, however, do not form a series and easily distinguished from each other and the other micas. Biotite is similar to muscovite in occurrence, with pegmatites being important sources for both minerals. The Feldspar Group might be regarded as varieties of a single mineral type. All members of this group are aluminum silicates of soda, potash, or lime.
Feldspars are the principal components of igneous rocks.
Orthoclase tends to be whitish while Microcline tends to be red-pink. Both are important constituents of granite. Microcline is usually encountered in every pegmatite. Soem forms of orthoclase have commercial value in ceramics and glass making. The Plagioclase Feldspars have Albite and Anorthite as end-members of a series.