Boleite with Gypsum

specimen number:
9273039

location:
Amelia Mine, Boleo, Baja California, Mexico

description:
A sharp lustrous blue crystal of boleite measuring 0.9 cm on edge set on matrix with gypsum. In great condition. Very fine example for the species.

The Amelia mine, situated near Santa Rosalia on the eastern coast of the Baja California Peninsula in Baja California Sur, Mexico, is a famous underground copper mine celebrated by collectors for producing exceptional specimens of boleite, pseudoboleite, and cumengeite. Geologically, this deposit is located within the unique El Boleo district, a stratiform, sediment-hosted copper-cobalt-zinc-manganese system where mineralization occurs within thin clay-rich tuffaceous sandstone layers, known as mantos, embedded within the Miocene-age Boleo Formation. Late-stage alteration of primary copper and lead sulfides by oxidising, chlorine-rich marine waters and meteoric fluids led to the precipitation of these rare, well-crystallized complex copper-lead halides within small fractures and open vesicles. Historically, mining in the region began following the discovery of copper oxide ores in 1868, with French interests organizing the massive Compagnie du Boleo in 1885 to systematically extract the ore through a sprawling network of underground workings, including the Amelia sector, which operated heavily through the late nineteenth and early twentieth centuries. Large-scale French operations ceased in 1954, after which local Mexican cooperatives ran intermittent, small-scale mining until the 1980s, followed by modern corporate reprocessing and open-pit development of the broader district in the twenty-first century.

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