Neptunite

specimen number:
2282015

location:
Mina Numero Uno, San Benito Co., California, USA

description:
Lustrous prismatic crystals of neptunite to 1.0 cm in length on matrix. Neat locality example, this is not from the usual locality for the species in this area. In good condition.

The Mina Numero Uno, situated in the Clear Creek area of the New Idria district within San Benito County, California, is a historic underground operation recognized for its specialized mercury and gemstone mineralizations. Geologically, the mine is hosted within a highly sheared tectonic melange of the Franciscan Complex, dominated by a massive, fault-bounded body of serpentinized peridotite that was subjected to intense late-stage hydrothermal alteration. This geologic environment produced localized veins and fracture fillings containing dense cinnabar concentrations alongside rare barium-titanium silicates like benitoite, joaquinite, and neptunite embedded in natrolite-rich matrices. Small-scale exploration and mining on the claim began around the late 1950s and picked up during the 1960s as miners extracted cinnabar ore for mercury production and targeted the pockets for premium crystal specimens. Commercial mining and organized excavation on the property gradually ceased by the late 1970s and early 1980s as mercury prices plunged and federal land use restrictions over the surrounding asbestos-rich hazardous zone closed the district to standard industrial development.

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