Azurite with Dickite

specimen number:
2282097

location:
Milpillas Mine, Cuitaca, Sonora, Mexico

description:
Lustrous blue bladed crystals of azurite slightly translucent and measuring to 1.1 cm in size on a matrix covered by white crystalline dickite. In good condition. Great color contrast.

The Milpillas mine, located in the Santa Cruz Municipality of northern Sonora, Mexico, is an underground copper operation known for its deeply developed secondary oxidation zone. Geologically, the deposit is a porphyry copper system that underwent millions of years of supergene enrichment, weathering low-grade primary copper sulfides into high-grade copper carbonates and oxides. This enriched zone was later buried and protected from surface erosion by a thick sequence of gravel deposits within a down-faulted graben, which preserved the mineralized structures until modern exploration located the covered deposit. The underground workings have produced significant quantities of azurite, malachite, brochantite, and chrysocolla within vugs and fractures in the host rocks. Commercial mining operations commenced at the site in 2006 under Industrias Penoles, utilizing a leaching and solvent extraction-electrowinning plant to process copper cathodes. Due to high operating costs and low commodity prices, underground ore extraction was suspended in 2020, though leaching of existing material continued until restricted mining and crushing activities were resumed in 2022.

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