Actinolite

specimen number:
2262295

location:
Wrightwood, San Bernardino Co., California, USA

description:
Good example for the species with green prismatic lustrous crystals of actinolite throughout matrix.

The Wrightwood mining district, located within the San Gabriel Mountains in western San Bernardino County, California, was a minor underground exploration and quarrying area primarily developed for gold, silver, and industrial limestone. Geologically, the area is situated within a highly complex tectonic zone adjacent to the San Andreas Fault, where Precambrian to Paleozoic metamorphic rocks, including schists, gneisses, and massive marble lenses, were intruded by Mesozoic granitic plutons. Hydrothermal fluids moving through these major fault zones and shear systems precipitated localized auriferous quartz veins containing pyrite, arsenopyrite, and minor base metal sulfides, while contact metamorphism transformed local sedimentary sequences into high-purity crystalline limestone deposits. Historically, gold was discovered in the nearby Swarthout Canyon area in the late nineteenth century, triggering localized prospecting and the development of small-scale underground workings such as the Big Horn Mine on the slopes of Mount Baden-Powell. Systematic mining and quarrying activities operated intermittently from the 1890s through the 1930s, but the structurally disrupted nature of the ore bodies, coupled with low grade consistency and high transportation costs in the rugged mountain terrain, prevented the district from achieving major long-term commercial success, leading to the permanent abandonment of all active mining operations prior to World War II.

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