What is Muscovite?
> Muscovite is the most common mineral of the mica family. It is an important rock-forming mineral present in igneous, metamorphic, and sedimentary rocks. Like other micas it readily cleaves into thin transparent sheets. Muscovite sheets have a pearly to vitreous luster on their surface. If they are held up to the light, they are transparent and nearly colorless, but most have a slight brown, yellow, green, or rose-color tint. The ability of muscovite to split into thin transparent sheets - sometimes up to several feet across - gave it an early use as window panes. In the 1700s it was mined for this use from pegmatites* in the area around Moscow, Russia. These panes were called "muscovy glass" and that term is thought to have inspired the mineral name "muscovite."
Sheet muscovite is an excellent insulator, and that makes it suitable for manufacturing specialized parts for electrical equipment. Scrap, flake, and ground muscovite are used as fillers and extenders in a variety of paints, surface treatments, and manufactured products. The pearlescent luster of muscovite makes it an important ingredient that adds "glitter" to paints, ceramic glazes, and cosmetics.
Muscovite has an anisotropic crystal structure, with two optical axis and a negative optical sign. The images and video taken with a polarization microscope with crossed polarizers and the Bertrand lens in place, are showing interference images (without lambda filter) in the plane perpendicular to the bisector between the two optical axes. To obtain these images, a thin slice of muscovite was split off from the crystal and taken for examination. Light entering this slice of crystal, produces the typical interference images for this type of crystal.
Anisotropic: material properties are directionally dependent
Igneous rocks are formed from the solidification of molten rock material.
Metamorphic rocks have been modified by heat, pressure, and chemical processes.
Pegmatites are rocks that form during the final stage of magma’s crystallization.