Brookite

Formula:  TiO2

Origin of name:  For Henry Brooke, English mineralogist

 

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:  Possible on {120}

Unit cell: a = 5.456 Ǻ, b = 9.182 Ǻ, c = 5.143 Ǻ

 

Colour:  Light brown to dark brown, dark reddish brown, black

Diaphaneity:

Luster:  Adamantine to submetallic

Habit:  Crystals tabular, vertically striated, varied habit

Hardness:  5.5 to 6

Specific gravity:  4.14

Cleavage:  2; {120} indistinct, {001} traces

Tenacity:  Subconchoidal to uneven; brittle

Streak:  White to gray or yellow

 

Synonyms/varieties:

 

Comments:  Trimorphous with anatase and rutile

 

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