Quartz

Unknown Owner

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An attractive example of what is known as Bruneau Jasper. cut and polished on one side. Quite attractive. Bruneau Canyon, located in Owyhee County, Idaho, is a deep river gorge carved through thick layers of Miocene volcanic rock, famous for hosting a highly distinctive variety of orbicular jasper known as Bruneau jasper. Geologically, this jasper formed within the rhyolite lava flows of the Bruneau-Jarbidge eruptive center, part of the Yellowstone hotspot track. Silica-rich fluids filled vesicular cavities and fractures in the cooling rhyolite, slowly precipitating microcrystalline quartz and chalcedony along with iron and manganese oxides that created characteristic brown, cream, and red egg-patterned bands. Commercial mining and quarrying along the steep canyon walls began following its discovery in the 1950s, with organized extraction operating primarily from the 1960s through the late 1990s. Active mining largely ceased after the turn of the century due to hazardous terrain, environmental regulations, and land access restrictions, leaving the locality officially closed today.