Cumengeite on Boleite
specimen number:
2262127
location:
Amelia Mine, Boleo, Baja California Sur, Mexico
description: The Amelia Mine, located within the famous Boleo District near Santa Rosalia in Baja California Sur, Mexico, is a world-renowned locality for rare copper and lead halides. Geologically, the deposit is unique for its stratiform ore bodies hosted in Pliocene-aged sedimentary rocks, specifically within clay-rich tuffaceous sandstones and conglomerates where seawater interaction with volcanic material facilitated the precipitation of unusual minerals. Cumengeite, a lead-copper-silver hydroxychloride, is the hallmark species of this site, typically forming spectacular indigo-blue, six-pointed star-shaped crystals that are often found as epitaxial overgrowths on boleite. Historically, mining and quarrying activities at the Amelia Mine were part of the extensive French-led Compagnie du Boleo operations, which began in the late 1880s and continued through the early 20th century. While the main industrial focus was the large-scale extraction of copper, the specific pockets of the Amelia Mine became legendary for producing the finest crystallized halides known to science. Although commercial production in the district transitioned and eventually declined by the mid-1900s, the locality remains a premier destination for mineralogical research.
Brilliant sharp blue crystals of cumengeite epitaxial up on a previous crystal of boleite. Classic material for this locality and species. In good condition. The specimen comes with a previous label from dealer Larry Conklin.
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