Rutile

Formula: TiO₂

Origin of name: from Latin rutilus = red

Crystal system: tetragonal

Crystal class: 4/m 2/m 2/m

Twinning: very common on {011} geniculated, elbow, contact, cyclic (sixlings or eightlings), also polysynthetic

Unit cell: a = 4.593 Å, c = 2.959 Å

Colour: reddish brown to red, yellow, orange-yellow, bluish, grayish black

Diaphaneity: 

Luster: adamantine to submetallic

Habit: crystals short prismatic, often striated along c-axis, slender prismatic to acicular, massive, compact to granular

Hardness: 6 to 6.5

Specific gravity: 4.23

Cleavage: 5; {110} and {100} distinct, {111} traces, {092} and {011} parting

Tenacity: conchoidal to uneven, brittle

Streak: pale brown to yellow

Synonyms/varieties:

Comments: trimorphous with anatase and brookite