Quartz with Pyrite

Unknown Owner

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Colorless gemmy crystals of quartz measuring to almost 2.5 cm in size coming off matrix with minor pyrite. In good condition. The Spruce claim, located in the Mount Si mining district of King County, Washington, is a famous mineral locality celebrated for producing world-class intergrown crystals of pyrite and quartz. Geologically, the deposit is hosted within highly altered Tertiary volcanic and sedimentary rocks of the Cascade Range, where high-temperature hydrothermal fluids associated with local plutonic intrusions created mineralization zones. These fluids filled open breccia zones and large subterranean cavities, or vugs, allowing exceptional combinations of lustrous, cubic and pyritohedral pyrite crystals to grow alongside elongated quartz prisms, including highly prized scepter and japan-law twin formations. Discovered and staked as a mining claim by private collectors in the late twentieth century, specifically around 1977, the site was never developed into a large-scale commercial industrial quarry or metal mine. Instead, it has been operated as a small-scale, seasonal hand-mining specimen operation by private claim owners and authorized collectors, with intermittent extraction activities continuing to yield high-quality mineral specimens for the collector market into the 2020s.