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Basal Cleavage
Muscovite and all other forms of mica are composed of flaky leaves of silicate material. The layers are stacked like pages in a book and can be peeled away as individual layers. Because of this property samples are often referred to as "books" of muscovite.
According to Dr. Helen Lang of West Virginia University, muscovite forms in low temperature felsic igneous rocks and in granite. Large cleavage plates of muscovite are sometimes used as windows in furnace and oven doors.
Color and Interference Color
Muscovite mica is readily identified by its white or light brown color. While muscovite may appear to be one color to the eye there are several other colors that will be seen under a microscope. This is because mica is an anisotropic mineral which means that different colors of light will be reflected from it depending upon the way the light is scattered by the mineral and the direction the light is traveling.
According to University Of North Dakota anisotropic minerals such as muscovite cause polarized light from the microscope to be scattered into two rays as it travels through a grain of the mineral. When the rays emerge from the grain they recombine to produce the interference colors.
Structure
Phyllosilicates such as muscovite are formed with a structure based upon interconnected silicon oxide tetrahedral rings that extend outward in layers. The rings are composed of one silicon atom and four oxygen atoms.
According to Tulane University, muscovite is a common element in aluminum-rich medium grade metamorphic rock and when grains of muscovite are ground down they produce a mottled bird's eye texture.