Anatase is Titanium Oxide,
Formula TiO2

Crystal system: Tetragonal (crystal shape commonly acute di-pyramidal.)
Hardness: 5.5 to 6.
Density: 3.9 gms/cm3
Colour: Typically yellow, brown, or bluish-black, Rarely colourless, green, blue or grey.
Streak: White to pale yellow.

Anatase is a secondary mineral, usually derived from other Titanium minerals. It is polymorphic with Rutile and Brookite.

It is widely distributed; well-known localities being Colorado, USA, Switzerland and Norway.

This specimen of Anatase on Quartz comes from Grisons, Switzerland, and shows clearly the acute di-pyramidal crystal shape and typical gunmetal blue colour.

Anatase on Quartz, Grisons, Switzerland.