Graphite

Formula:  C

Origin of name:   Form Greek for to write

Crystal system:   Hexagonal

Crystal class:  6/m 2/m 2/m

Twinning:  Probably on {11-21}; on {0001} due to pressure; also about [0001] axis

Unit cell: a = 2.463 Ǻ, c = 6.714 Ǻ

Colour:  Iron-black to steel-gray

Diaphaneity:

Luster:  Metallic, dull, earthy

Habit:   Crystals thin tabular, hexagonal; massive, fine to coarse foliated; radiate aggregates, columnar, granular, scaly, earthy

Hardness:  1 to 2

Specific gravity:  2.09 to 2.23

Cleavage:  1; {0001} perfect

Tenacity:  Flexible, inelastic; greasy

Streak:  Black

Synonyms/varieties:  Cliftonite (cube-shaped var.), plumbago

Comments:  Polymorphous with chaoite, diamond and lonsdaleite; data are for graphite-2H; there is also graphite-3R