Liebigite with Uranophane, Sklodowskite

specimen number:
2133316

location:
Schwartzwalder Mine, Jefferson Co., Colorado, USA

description:
Brilliant yellow green crystalline liebigite on matrix with yellow crystalline uranophane and sklodowskite. Very good example for the species. Classic locality for this species.

The Schwartzwalder mine, situated in Ralston Canyon northwest of Golden in Jefferson County, Colorado, is a geologically unique underground operation recognized as the largest single primary vein-type uranium deposit in the United States. The deposit is hosted within a complex structural setting consisting of Proterozoic metamorphic rocks, primarily garnet-biotite gneisses and schists, which were intensely fractured during the Laramide orogeny to form the major Rogers Fault system. Hydrothermal fluids moving through these structural breccias deposited primary pitchblende along with subordinate base-metal sulfides and carbonate gangue minerals in steeply dipping vein networks. Discovered in 1949 by Fred Schwartzwalder, the property saw its first commercial ore shipments in 1953 under the name Ralston Creek mine before being renamed. Corporate development expanded rapidly under Cotter Corporation, which acquired the site in 1965 and operated the underground mine continuously to supply fuel for the domestic nuclear industry. Production peaked during the 1970s and 1980s, but declining global uranium prices and environmental regulatory pressures led to a suspension of active mining in 2000.

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