Anatase

Chemical Formula : TiO₂
Hardness : 5.5-6
Cleavage : Three, prefect
Luster : Adamantine
Color : Yellowish and reddish brown to black
Streak : White to pale yellow
Density : 3.9
Diagnostic Features and Trivia :
Crystal System and Habit : Tetragonal; uncommon crystals are pyramidal {101} or tabular {001}
Twinning : None
Polymorphs : Brookite and Rutile
Index of Refraction : omega=2.561; epsilon=2.488