Mimetite after Wulfenite

specimen number:
2242065

location:
San Francisco Mine, Sonora, Mexico

description:
An interesting pseudomorph specimen, at one time this was a cluster of tabular wulfenite crystals. These are now completely replaced by crystallized yellow mimetite. Complete all around with very minimal damage on the backside of the piece only.

The San Francisco Mine, located near Magdalena de Kino in Sonora, Mexico, is a world-class mineral locality situated within the Basin and Range province. Geologically, the deposit is a lead-zinc-silver replacement system where hydrothermal fluids interacted with Mesozoic sedimentary rocks and later underwent extensive oxidation. The mine is most famous for producing what many consider the world's finest wulfenite specimens, characterized by bright orange, tabular crystals often found in striking aesthetic association with yellow to orange globular mimetite. Historically, mining and quarrying in the district began in the late 19th century, with the most significant period of specimen recovery occurring between the 1960s and 1990s as the mine was worked primarily for gold and silver. While large-scale industrial operations have transitioned over time, the site remains a legendary name for mineralogists and collectors due to the unique chemistry that allowed for such vibrant and well-crystallized secondary minerals. Geological interest in the oxidation zones of the Sonoran desert continues to make this site a reference point for lead-molybdate formation through 2026.

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