Heterogenite

Formula:  CoO(OH)

Origin of name:   From Greek for other and kind

Crystal system:  Hexagonal

Crystal class:  -3 2/m

Twinning: 

Unit cell: 

Colour:  Black, steel-gray 

Diaphaneity:  Opaque

Luster:  Metallic to dull

Habit:  Crystals acicular with hexagonal cross section, minute; massive, microcrystalline; botryoidal or mammillary crusts

Hardness:  4 to 5

Specific gravity:  4.13 to 4.47

Cleavage:  2; One parallel to elongation, one inclined

Tenacity: 

Streak:  Black, brownish black, dark brown

Synonyms/varieties:

Comments:  Data are for heterogenite-3R; there is also a -2H polytype