If you’re road-tripping through southwest Colorado with a high-clearance four-wheel drive, Cashin Mine is a must-visit! Brave the four-mile rocky road to visit the weathered buildings and abandoned workings from this historic copper-silver ore hotspot.
Molly Turko
Structural Geologist, Devon Energy
The Mine's History and Colorado Plateau Geology
Fracture damage zone (main fault indicated by yellow arrow)/ Photo courtesy of Molly Turko
Prospectors staked claims in the Cashin Mine during the 1890s, and they discovered rich copper-silver ore in 1897. This ore supported intermittent mining for much of the twentieth century.
Ore mined ranged from 7–12 percent Copper and 8–134 ounces of silver per ton. One shipment of native copper reached an astonishing 89 percent Copper!
Area geology: The Cashin Mine lies within the Colorado Plateau, a region characterized by sedimentary rocks deposited from the Paleozoic through the Mesozoic.
During the Late Triassic and Jurassic, vast deserts covered much of the area, creating the thick sandstones and red beds seen today.
Later uplift of the Colorado Plateau preserved these strata while Laramide tectonism and salt movement in the nearby Paradox Basin created faults and fractures that provided pathways for mineralizing fluids.
These structural features, combined with porous Jurassic sandstones, set the stage for the formation of the copper-silver deposits that would later be discovered at the Cashin Mine.
The deposit occurs in the Jurassic eolian (wind-blown dune) Wingate Sandstone along the Cashin Fault and is one of the best-known sediment-hosted copper deposits in the Paradox Basin.
Must-see geology during your visit:
Structural geology is king at Cashin, with much of the mineralization concentrated along faults, fractures, and surrounding damage zones.
High-angle normal faults, likely related to the collapse of the underlying salt anticline, controlled fluid flow by connecting the Wingate Sandstone to deeper fluid sources and focused mineralization.
The first of two major fluid events occurred during the Laramide, when hydrocarbons migrated along the Cashin Fault and into permeable sandstones, bleaching the red beds and replacing iron oxides with pyrite.
A second fluid event occurred during the mid- to late Tertiary, when oxidized copper-bearing fluids migrated upward along the Cashin Fault. The bleached sandstones, enriched in pyrite and hydrocarbons, acted as a chemical trap that caused dissolved copper to precipitate.
Go deeper: Learn more about the geology of the Colorado Plateau here.
Trip Tips: How to Plan Your Cashin Mine Roatrip
Photo courtesy of Molly Turko
Cashin Mine is just over an hour's drive from Moab, Utah, where you can find plenty of options for lodging, food, and other geological adventures. The drive to the mine is rocky, so a four-wheel drive vehicle with high clearance is a must. Plan your rental accordingly!
Note: The road to the mine is owned by the Bureau of Land Management, but the mine's existing structures are on private property, so you can look from the road, but you cannot enter the mine's remains. Admire the Colorado Plateau's geology on the way, then get out and take a peek, but stick close to your car!
