Diaspore

Chemical Formula : AlO(OH)
Hardness : 6.5-7
Cleavage : Two; one perfect, and one less perfect.
Luster : Brilliant vitreous, pearly on cleavages.
Color : White, grayish-white, colorless.
Streak : White
Density : 3.3-3.5
Diagnostic Features and Trivia : Diaspore is a common constituent of the earthy marix of Bauxite, but can also be found with corundum in emery rockm, and some crystalline limestones.
Crystal System and Habit : Orthorhombic; rarely forming crystals of thin plates or tabular along {010}.
Twinning :
Polymorphs : Boehmite
Index of Refraction : alpha=1.682-1.706; beta=1.705-1.725; gamma=1.730-1.752.