Calomel

Formula:  Hg₂Cl₂

Origin of name:  From Greek kalos - good and melas - honey

Crystal system:  Tetragonal

Crystal class:  4/m 2/m 2/m

Twinning:

Unit cell: a = 4.480 Ǻ, c = 10.91 Ǻ

Colour:  Colourless, white to yellowish gray, gray, brown

Diaphaneity:

Luster:  Adamantine

Habit:  Crystals tabular, pyramidal, prismatic, equant, often complex; crusts, earthy masses

Hardness:  1.5

Specific gravity:  7.16

Cleavage:  2; {110} good, {011} imperfect

Tenacity:  Conchoidal; sectile, plastic

Streak:

Synonyms/varieties:

Comments:  Series with kuzminite; fluoresces dark red