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CALIFORNIA

Lost Turquoise Mine of Slocum Mountain

GEOLOGY OF THE AREA

Slocum Mountain and the majority of the surrounding hills are mostly composed of highly weathered Mesozoic-age granitic rock. A few small exposures of Tertiary volcanic rocks occur on Slocum Mountain; much larger exposures of similar rock crop out 10 miles northwest of Slocum Mountain at Eagle Crags. To the south of Slocum Mountain, in the Opal Mountain/Black Mountain area, Miocene volcanic and pyroclastic rocks and younger Pleistocene basalts are abundant.

A few miles west of Slocum Mountain lie a series of heavily weathered and dissected hills that extend roughly 7 miles in a northwest-southeast direction. These small hills are composed of hypabyssal Tertiary-age rhyolite. But again, most of the underlying bedrock in the area consists of Mesozoic granitic rock. The heavily weathered granite is ideal host rock for veinlets and nodules of turquoise.

PROSPECTING POTENTIAL

Turquoise is found only in the oxidized zone of primary copper deposits, usually within about 150 feet of the surface. It almost invariably occurs in arid regions and is generally associated with silicic igneous rocks like granite, rhyolite, and trachyte. Extreme alteration of the host rock combined with copper and phosphorus-rich fluids produces an environment conducive to the formation of turquoise deposits. Slocum Mountain and most of the surrounding hills are predominantly composed of highly weathered granitic rock.

This is ideal host rock for veinlets and nodules of turquoise. Prospectors may want to concentrate on the western slopes of Slocum Mountain. The Morrow brothers' account places the mine on a low ridge or hillock on the west side of the mountain, and this is certainly as good a place as any to start. Prospectors should realize that Slocum Mountain lies just inside the China Lake Naval Weapons Center. Permission is required to enter this facility.