Muscovite.
http://www.mineralszone.com/minerals
A group of minerals having perfect basal cleavage and capable of splitting into thin laminae is called mica. Chemically they contain complex silicate of aluminium and alkalies with hydroxyl. They crystallize in monoclinic system. Some varieties may contain iron, magnesium, lithium and rearely fluorine, barium, manganese and vandium. There are seven important mica minerals: * Muscovite or potassium mica
H2KAl3(SiO4)3
* Paragonite or sodium mica
H2NaAl3(SiO4)3
* Lepidolite or lithium mica
K Li Al(OH, F)2Al(SiO4)3
* Phlogopite or magnesium mica
H2KMg3Al(SiO4)3
* Biotite or magnesium iron mica
(H2K)(Mg, Fe)3Al(SiO4)3
* Zinnwaldite or lithium iron mica
Li2K2Fe2Al4Si7O24
* Lepidomelane or iron mica
(H, K)2(Fe, Al)4(SiO4)5 Muscovite is the commonest of all and whenever the word mica is used it is understood to mean muscovite.
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