BIOTITE

K (FE, Mg)3 AlSi3 O10 (F, OH)2
Potassium iron magnesium aluminum silicate hydroxide fluoride

 Cleavage: perfect in one direction, flakes

 Colour: possible and observed colours

 Fracture: not readily observed due to cleavage, uneven

 Hardness: 2.5

 Luster: vitreous to pearly

 Streak: white

 Possible Useage:

 More Info: Mineral Gallery, Mineralogy Database