Adamite is a Zinc Arsenate Hydroxide mineral with Zn2(AsO4)(OH) formula. It belongs to the Olivenite Group of minerals. The yellow to bright lime-green colored crystals and druze, along with its distinctive fluorescence, make adamite a favorite among mineral collectors. Adamite occurs in many different lively colors. Pure adamite is colorless but usually it possesses a yellow color due to traces of iron. It may also be greenish yellow, green, greenish blue, sky blue, pink, purple, orange, or rarely white or red. Sometimes multicolored. Different impurities are responsible for the color types. When copper is present in Adamite, this gives a vibrant green or blue color; when cobalt is present, it gives a pink to purple color. It is well-known for its green or yellow-green fluorescence in short or long-wave ultraviolet light.
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. 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. Adamite crystals are frequently embedded in rusting, crumbly, brown Limonite matrices that stain the hands.
Crystal forms include clusters of short, stubby crystals but sometimes occur in elongated prisms, usually in groupings. Also occurs as acicular, radiating, and globular. Crystals are usually transparent to translucent.
Adamite belongs to the Orthorhombic Crystal System, the Dipyramidal Crystal Class. Hardness is 3.5 on the Mohs Scale, while Specific Gravity is 4.3 – 4.5. Luster is vitreous. Paradamite is the triclinic dimorph of Adamite, meaning that they have the same chemical formula but crystalize in different crystal systems.
Varieties of Adamite:
Cobaltoadamite – Adamite contains cobalt in its structure, which replaces some of the zinc. The presence of cobalt gives this variety a purple color.
Cuproadamite – Adamite contains copper in its structure, which replaces some of the zinc. The presence of copper gives it a vibrant blue-to-green color.
Adamite forms a solid solution series with the copper arsenate mineral Olivenite and the intermediate, structurally distinct member Zincolivenite. Zincolivenite, a new mineral name approved by the IMA in 2006, is now a recognized mineral specimen that contains an intermediary amount of copper and zinc.
The most significant occurrence for Adamite is the Ojuela Mine in Mapimi, Durango, Mexico, where large, beautiful, and highly fluorescent examples occur in all different colors. Other important occurrences are Lavrion, Greece; Cap Garonne, France; Tsumeb, Namibia; the Brenner Mine, Dal’negorsk, Russia; and Nandan, Guangxi, China.
In the United States, the best occurrence is Gold Hill, Tooele County, Utah. Small colorless crystals were also found at Chloride Cliff in Death Valley, Inyo County, California.
By Bill Jones, Sidewinder Minerals