Anatase

Formula:  TiO₂

Origin of name:  From Greek for elongation

Crystal system:  Tetragonal

Crystal class:  4/m 2/m 2/m

Twinning:  rare on {112}

Unit cell:   a = 3.785 Å, c = 9.514 Å

Colour:  Brown, deep blue, black; colourless, gray, green, blue

Diaphaneity: Transparent when lightly coloured to nearly opaque when dark coloured

Luster:  Adamantine or metallic-adamantine

Habit:  Crystals steep pyramidal, often striated at right axis angles to c-axis; blunt pyramidal, tabular, prismatic

Hardness: 5.5 to 6

Specific gravity:  3.82 to 3.97

Cleavage:  2; {001} and {011} perfect

Tenacity:  Brittle

Streak:  Colourless, white, to pale yellow

Synonyms/varieties:  Dauphinite, hydrotitanite, octahedrite, wiserine

Comments:  Trimorphous with rutile and brookite. Uusally formed as secondary mineral, derived from other titanium-bearing minerals. In Alpine veins, derived from the enclosing gneisses or schists by hydrothermal solutions. In igneous and metamorphic rocks; in pegmatites; from a carbonatite. A common detrital mineral in sediments.