Laurionite

Formula:  PbCl(OH)

Origin of name:  Locality; Laurium, Greece

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning: 

Unit cell: a = 7.11 Ǻ, b = 9.7 Ǻ, c = 4.06 Ǻ

Colour:  Colourless, white

Diaphaneity: 

Luster:  Adamantine, silky, pearly on {100}

Habit:  Crystals thin to thick tabular

Hardness:  3 to 3.5

Specific gravity:  6.24

Cleavage:  1; {101} distinct

Tenacity: 

Streak: 

Synonyms/varieties:

Comments:  Dimorphous with paralaurionite