Murdochite with Aurichalcite

specimen number:
2282060

location:
Ojuela Mine, Mapimi, Durango, Mexico

description:
Very rich sparkling black crystals of murdochite on matrix with sky-blue aurichalcite. In great condition, very good example for the species.

The Ojuela mine, located near the town of Mapimi in Durango, Mexico, is a major carbonate replacement deposit situated within the Sierra de Mapimi range. Geologically, the deposit consists of an intricate network of hydrothermal replacement bodies, mantos, and chimneys hosted within heavily faulted and folded Cretaceous limestones of the Aurora Formation. The primary mineralization was driven by mid-Tertiary igneous intrusions, which released metal-rich hydrothermal fluids that dissolved the limestone and deposited massive lead, zinc, and silver sulfides, which later underwent extensive oxidation to create an incredibly diverse assemblage of secondary arsenates, carbonates, and oxides within deep solution cavities. Discovered by Spanish explorers in 1598, the mine saw centuries of primitive surface and shallow underground extraction before being modernized in the late nineteenth century by the Compania Minera de Penoles, which constructed a massive infrastructure including the famous Ojuela suspension bridge. Industrial-scale production of base and precious metals continued aggressively until the late 1930s when rising water levels and the exhaustion of major sulfide bodies led to the cessation of corporate operations, though the mine has remained active into the twenty-first century through local cooperative miners who carefully extract mineral specimens from the vast oxidized zones.

Murdochite is a secondary copper lead halide oxide mineral that typically develops as a product of alteration within the deeply oxidized zones of polymetallic base-metal deposits. Geologically, it forms under highly alkaline and arid oxidizing conditions where copper and lead solutions interact with chloride ions from surface waters or arid soils, often appearing in close association with other secondary species like plattnerite, hemimorphite, aurichalcite, and malachite. The mineral typically manifests as opaque, isotropic, jet-black to brownish-black microcrystals that exhibit a distinct metallic to adamantine luster, commonly forming as tiny cubes, octahedrons, or velvety drusy coatings lining the internal cavities of gossan matrices.

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