Adamite

Formula:  Zn₂(AsO₄)(OH)

Origin of name:  for Gilbert Joseph Adam (1795-1881), French mineralogist, supplied the first specimens

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:

Unit cell:  a = 8.31 Å, b = 8.51 Å, c = 6.04 Å

Colour:  Light yellow, honey yellow, yellowish green, brownish yellow, may be zoned

Diaphaneity: Transparent to translucent

Luster:  Vitreous

Habit:  Crystals varied, commonly elongated along b-axis, tabular or equant, drusy

Hardness:  3.5

Specific gravity:  4.32 to 4.48

Cleavage:  2; {101} good; {010} poor

Tenacity:  Brittle

Streak: White

Synonyms/varieties:

Comments:  Dimorphous with paradamite; series with olivenite. Found as a secondary mineral in the oxidised zone of zinc- and arsenic-bearing hydrothermal mineral deposits.