Lemanskiite

specimen number:
2133404

location:
Guanaco Mine, Taltal, Antofagasta, Chile

description:
Good thumbnail for the species, rich brilliant blue micro crystals on matrix.

The El Guanaco mining district (which includes operations like the Abundancia mine), situated near Taltal in the Antofagasta Province of Chile, is a historic gold and copper mining locality known for its rich epithermal vein systems. Geologically, the deposit is hosted within upper Cretaceous to Paleocene volcanic rocks, where intense hydrothermal alteration created structurally controlled quartz veins rich in gold, enargite, and secondary copper-arsenic minerals. High-grade gold mineralization was first discovered in the district in the late 1870s, prompting a major mining rush that peaked during the 1880s and 1890s. While primary deep extraction slowed down by the early twentieth century due to ore depletion, the district has experienced intermittent revivals, including modernized open-pit heap leaching operations targeting gold and silver from the late twentieth century into the early 2000s.

Lemanskiite is a hydrous sodium, calcium, and copper chlorarsenate mineral that crystallizes in the monoclinic system, typically forming as a secondary mineral in the oxidized zones of copper-arsenic deposits. Geologically, it develops as a low-temperature weathering product, occurring on mine walls and dump material where it is associated with minerals like lammerite, olivenite, and quartz under highly acidic environmental conditions. The mineral is visually distinctive, characteristically forming rosette-shaped aggregates or dense nodules up to five centimeters long that exhibit a striking dark sky-blue to electric-blue color and a vitreous luster. Initially discovered at the Abundancia mine within the El Guanaco district and named after American mineral collector Chester Lemanski, it features a low Mohs hardness of approximately 2.5 and perfect cleavage parallel to the base of the crystal structure.

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