Number 27

Color--------------------Black to Dark brown

Luster------------------Nonmetallic, glassy to pearly

Streak------------------White

Hardness--------------2.5

Cleavage/-------------Cleavage, perftect basal
Fracture                   cleavage

S.G.---------------------2.8 - 2.9

Special Properties---Shows similar physical properties to muscovite except black in color.

Formula-----------------K(Mg, Fe)3(AlSi3O10)(OH)2

Mineral Name---------Biotite

Family-------------------Silicates

Uses---------------------Very common rock forming mineral.

Biotite