Adamite

This article is about the mineral. For the religious sect, see Adamites.

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. tarbuttite is an analogous zinc phosphate.

Adamite on limonite from the Gold Hill District Tooele County, Utah, US. Scale at bottom is c. 2.5 cm.

Adamite
Yellow-green adamite in limonite
General
Category	Arsenate mineral
Formula	Zn2AsO4OH
IMA symbol	Ad[1]
Strunz classification	8.BB.30
Dana classification	41.06.06.03 Olivenite group
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H–M symbol: (2/m 2/m 2/m)
Space group	Pnnm
Identification
Color	Pale yellow, honey-yellow, brownish yellow, reddish; rarely white, colorless, blue, pale green to green, may be zoned
Crystal habit	Wedge-like prisms typically in druses and radiating clusters; also smooth botryoidal masses
Cleavage	{101}, good; {010}, poor
Fracture	Uneven to subconchoidal
Tenacity	Brittle
Mohs scale hardness	3.5
Luster	Vitreous
Streak	White to pale green
Specific gravity	4.32–4.48 measured
Optical properties	Biaxial (+/−)
Refractive index	nα=1.708 – 1.722, nβ=1.742 – 1.744, nγ=1.763 – 1.773
Birefringence	δ = 0.055
Other characteristics	May fluoresce and phosphoresce lemon-yellow under SW and LW UV.
References	[2][3][4]

Occurrence

Adamite occurs as a secondary mineral in the oxidized zone of zinc- and arsenic-bearing hydrothermal mineral deposits. It occurs in association with smithsonite, hemimorphite, scorodite, olivenite, calcite, quartz and iron and manganese oxides.^[2]

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

Adamite was named after the French mineralogist Gilbert-Joseph Adam (1795–1881). It was first described in 1866 for an occurrence at the type locality of Chañarcillo, Copiapó Province, Atacama Region, Chile.^[3]

See also

• List of minerals
• List of minerals recognized by the International Mineralogical Association
• List of minerals named after people