Quartz with Dolomite, Pyrite

specimen number:
2292424

location:
Spruce Claim, King Co., Washington, USA

description:
Nice combination piece showing a glassy gem colorless crystal of quartz hosting crystallized dolomite and bright golden pyrite. In good condition.

The Spruce Claim, located on Spruce Ridge in King County, Washington, is a classic mineral locality situated within the Snoqualmie Batholith, a large intrusive igneous body of Oligocene to Miocene age (approximately 25 million years old). Geologically, the deposit resides inside an intrusive breccia pipe, a vertical chimney formed when highly pressurized, escaping volcanic gases shattered the cooling granodiorite country rock. Subsequent hydrothermal fluids circulating through the open spaces of the breccia deposited large quartz crystals alongside iron sulfides, specifically pyrite, on the walls of the rock cavities. Historically, the area was first explored during copper mining booms in the early twentieth century. However, the locality became renowned for specimen mining rather than industrial metals, particularly after geologist Bob Jackson and others formally claimed and worked the site starting in the late 1970s.

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