Neptunite

specimen number:
2063203

location:
California State Gem Mine, San Benito Co., California, USA

description:
The top of this natrolite coated matrix is scattered nicely with lustrous black prismatic terminated crystals of neptunite measuring to 2.0 cm in length. This is in very good condition with minimal damage present as seen. Classic material for the species and locality. The specimen comes with a previous label from the collection of Ray DeMark.

The California State Gem Mine, originally known as the Dallas Gem Mine, was discovered in 1907 by prospector James Marshall Couch and operated intermittently under various owners before commercial mining ceased in 2005, after which the property transitioned to a fee-digging and specimen-collecting site. Geologically, the deposit is situated in the New Idria district of the Diablo Range within San Benito County, where tectonic activity emplaced a large serpentinite body alongside blocks of blueschist belonging to the Franciscan Complex. The rare gem crystals formed within hydrothermal veins of white natrolite that cut through the glaucophane schist, representing a unique metamorphic environment created during ancient subduction processes.

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