Dunn-Seiler Museum specimen

Muscovite mica is a phyllosilicate mineral with the chemical formula of KAl₂(AlSi₃O₁₀)(F,OH)₂. It is the most common mica mineral, often found in igneous rocks such as granite, or metamorphic rocks such as schist. It has a pseudo-hexagonal crystal structure and perfect basal cleavage, which means that it breaks in flat sheets along a single plane. This, in combination with its transparency, allowed it to be used as an alternative to glass window panes in the past. It is also known to be a good insulator and has been used in fireplaces and for fireproofing.