FELDSPAR

Chemical Composition: NaAlSi3O8(albite) and CaAl2Si2O8(anorthite) and all compositions between.

Hardness: 6-6.5

Color: White to dark gray.

Specific Gravity: 2.6-2.7

Cleavage Planes: Two perfect, not quite at right angles. May show fine parallel striations which distinguish it from potassium feldspar.

Crystal Structure: Irregular grains. Tabular crystals.

Luster: Nonmetallic