Vanadinite

specimen number:
2282048

location:
Old Yuma Mine, Pima Co., Arizona, USA

description:
Orange red crystals of vanadinite measuring to 0.5 cm in size on matrix. In good condition, nice for this classic locality.

The Old Yuma mine, situated in the Amole District of the Tucson Mountains in Pima County, Arizona, is a historic underground deposit noted for its diverse suite of secondary lead, molybdenum, and vanadium minerals. Geologically, the mineralization is hosted within the Cretaceous Amole Arkose and associated volcanic units, where northwest-trending fault fissures were invaded by hydrothermal solutions during Laramie-age igneous activity. These fluids deposited primary sulfides, chiefly galena, wulfenite, and vanadinite, which subsequently underwent profound oxidation to form exceptional, well-formed crystals of bright orange wulfenite and deep red vanadinite within open vugs and fractured vein zones. Prospecting at the site began around 1885, but formal production occurred intermittently from 1916 through 1920 under the direction of the International Ore Separation Company, which erected a concentration mill to process lead and molybdenum ores. Underground mining largely ceased by World War II due to depleted ore shoots, though the property was worked sporadically by private collectors for mineral specimens throughout the mid-to-late twentieth century until being incorporated into the expansion areas near the Saguaro National Park boundary.

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