There are various forms of mica, including muscovite, lepidolite, biotite and phlogopite. The chemical formula for Muscovite Mica, the most common form, is KAl3Si3O10(OH)2 (please note, all numbers are subscripts). The other chemical formulas for mica are: lepidolite K(Li,Al)3(AlSi3O10) (O,OH, F)2, biotite K(Mg, Fe)3(AlSi3O10) (OH)2 and phlogopite KMg3(AlSi3O10) (OH)2.
The chemical formula for muscovite translates to one potassium atom, three atoms of aluminum, three silicon atoms, ten oxygen atoms and two bonded oxygen/hydrogen molecules attached in two different places within the mica compound. An alternate chemical formula consists of chromium (Cr) or manganese (Mn) replacing aluminum atoms within the compound: K(Al,Cr,Mn)3Si3O10(OH)2. Again, all numbers are subscripts representing the number of atoms for the preceding symbol (for example, Si3 is the same as three silicon atoms).