Adamite

Adamite,

Adamite
General
Chemical formula	Zn₂AsO₄OH
Identification
Color	Yellow, green, rarely white, and occasionally purple
Crystal habit	Wedge-like prisms typically in druses and radiating clusters - also smooth botryoidal masses.
Crystal system	Orthorhombic; 2/m 2/m 2/m
Cleavage	perfect in two directions
Fracture	conchoidal
Mohs Scale hardness	3.5
Luster	adamantine
Refractive index	nα=1.708 - 1.722, nβ=1.742 - 1.744, nγ=1.763 - 1.773
Streak	white to pale green
Specific gravity	4.4
Other Characteristics	Strongly fluoresces green in short and long UV light.

Adamite is a zinc arsenate hydroxide mineral, Zn₂AsO₄OH. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Pure adamite is colorless, but usually it possess yellow color due to Fe compounds admixture. Tints of green also occur and are connected with copper substitutions in the mineral structure. Olivenite is a copper arsenate that is isostructural with adamite and there is considerable substitution between zinc and copper resulting in an intermediate called cuproadamite. Zincolivenite is a recently discovered mineral being an intermediate mineral with formula CuZn(AsO₄)(OH). Manganese, cobalt, and nickel also substitute in the structure. An analogous zinc phosphate, tarbuttite, is known.

The yellow to bright lime-green colored crystals and druze along with its distinctive fluorescence make adamite a favorite among mineral collectors. Found in Mapimi, Mexico; Greece; and California and Utah in the United States.

Adamite was named after the French mineralogist Gilbert Joseph Adam (1795-1881). The type locality is in the Atacama Desert in Chile.
See also

* A comprehensive list of minerals
* List of minerals named after people

References

List of minerals