Gold-quartz hydrothermal vein - here's a nice gold ore sample from a quartz-gold vein in southwestern Colorado's Telluride Mining District.  This is from the Smuggler Vein, which cuts through Oligocene- and Miocene-aged rhyolites, andesites, and volcanic tuffs of the San Juan Formation, a thick unit of extrusive igneous rocks in the San Juan Volcanic Field.

The Smuggler Vein is one of several mineralized veins developed along steeply-dipping fractures formed during volcanic-related uplift in the Silverton, Colorado area and the Stony Mountain, Colorado area.  Uplift & fracture formation occurred during the mid-Oligocene, followed by gold mineralization during the late Early Miocene.

Geologic Unit & Age: Smuggler Vein, San Juan Volcanic Field, gold-quartz hydrothermal mineralization in the late Early Miocene, ~17 million years.

Locality: Smuggler-Union Consolidated Mine (Smuggler Mine), Telluride Mining District (a.k.a. Upper San Miguel District), eastern San Miguel County, southwestern Colorado, USA

(CSM # 54581, Colorado School of Mines Geology Museum, Golden, Colorado, USA)



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