Malachite-Azurite after Gypsum

specimen number:
2292206

location:
Apex Mine, Washington Co., Utah, USA

description:
A classic specimen from Utah, this a combination of green malachite and blue azurite these forming a cast after a now gone crystal of gypsum. This is classic old material for this locality.

The Apex mine, located in the Beaver Dam Mountains of Washington County, Utah, is a historically significant underground deposit known for its complex supergene mineralization, eventually operating as the world first exclusive producer of gallium and germanium. Geologically, the deposit is a pipe-like breccia zone hosted within the Mississippian-age Callville Limestone, where faulting allowed primary copper, lead, zinc, and iron sulfides to undergo intense oxidation, leaving behind a rich suite of secondary azurite, malachite, jarosite, and iron oxides enriched with rare metals. Discovered in 1884, the site saw initial copper mining and sporadic production by the Dixie Mining Company and other operators until the 1940s, with a major industrial resurgence occurring between 1985 and 1987 when Musto Explorations refurbished the underground workings to extract gallium and germanium before fluctuating metal prices led to a suspension of primary corporate operations.

Within the upper oxidation zones of this deposit, unique pseudomorphic casts formed when original, well-developed monoclinic gypsum crystals were completely dissolved away by altering meteoric fluids, leaving distinct hollow molds within the surrounding iron-rich matrix. Over time, subsequent carbonate-rich fluids flowing through these open cavities slowly precipitated vibrant blue azurite and green malachite along the interior walls, perfectly preserving the sharp, angular crystal shapes of the long-gone gypsum precursors.

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