Arzakite

Formula:  Hg₃S₂(Br, Cl)₂

Origin of name:  After locality, Arzak deposit, Tuva, Russia

Crystal system:  Monoclinic or triclinic

Crystal class: 2 or m or 2/m

Twinning:

Unit cell: a = 8.99 Å, b = 5.24 Å, c = 18.45 Å, b = 92.28°

Colour:  Colourless to yellow

Diaphaneity: Transparent

Luster:  Vitreous to adamantine

Habit: As complex intergrowth to 0.2 mm

Hardness:  2 to 2.5

Specific gravity:  7.64 (calculated)

Cleavage:  None

Tenacity:

Streak:

Synonyms/varieties:

Comments:  Series with lavrentievite; dimorphous with grechishchevite. Found in the oxidised zone of a hydrothermal deposit