Catalog Search Guide
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Conichalcite
Conichalcite is a calcium copper arsenate, CaCu(AsO4)(OH), prized by collectors for its vivid grass-green to apple-green botryoidal crusts and reniform masses. It belongs to the adelite-descloizite group and forms solid-solution series with austinite, duftite, and tangeite, making it an interesting species for those studying arsenate-vanadate chemistry. It typically forms in the oxidized zones of copper orebodies, where oxygen-rich groundwater alters primary sulfides, and is commonly found intergrown with malachite, azurite, smithsonite, adamite, and olivenite on limonitic matrix.
The species was first described in 1849 from the Don Bonete mine near Hinojosa del Duque in Córdoba, Spain, its type locality. The finest and most sought-after specimens, however, come from the Tsumeb Mine in Namibia, celebrated for sharp, lustrous crystal groups on contrasting matrix. Other classic sources include the Ojuela Mine in Mapimí, Mexico, numerous copper districts of Utah, Arizona, and Nevada in the United States, the Dome Rock Copper Mine in South Australia, and occurrences across Chile, England, and Poland.
Collectors value conichalcite for its saturated green color, unusual acicular and hemispherical crystal aggregates, and its role as a diagnostic secondary copper-arsenate in classic oxidation-zone assemblages. Well-formed crystals are rare, so cabinet-grade pieces with bright, glassy botryoidal crusts from Tsumeb or Ojuela are especially desirable for thumbnail and miniature mineral collections.
