What is Muscovite?
Muscovite makes the architecture of a silicate visible. A single flake can split into elastic transparent sheets, while a large pegmatite plate or schist foliation shows how mica controls the texture of an entire rock.
Mineralogy and crystal structure
Reference formula: KAl2(AlSi3O10)(OH)2. Muscovite is a monoclinic dioctahedral mica with perfect basal cleavage. Thin elastic sheets, reflective surfaces and colour variation are direct expressions of its layered structure; chromium-rich varieties such as fuchsite and mariposite should be labelled as varieties. Muscovite is classified with silicates and has a monoclinic crystal system. Typical hardness is 2–2.5 on the Mohs scale and specific gravity is approximately 2.7–3.1.
Colour, lustre and habit
Typical colours include colourless, silver, brown, green, pink. The usual platy, foliated, micaceous habit and pearly, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Muscovite forms in or is associated with granitic pegmatites, mica schists, gneisses, hydrothermal alteration zones and weathering profiles. Important documented localities include Brazil, India, Russia, Madagascar, the United States, Canada and Norway.
Reflective sheets from granite and schist
Muscovite makes the architecture of a silicate visible. A single flake can split into elastic transparent sheets, while a large pegmatite plate or schist foliation shows how mica controls the texture of an entire rock.
Collecting and care
Very soft and cleavable: keep sheets flat or supported, away from water, abrasion and pressure.
