Silver Reef Mining District, Washington County, Utah, USAi

Regional Level Types
Silver Reef Mining District	Mining District
Washington County	County
Utah	State
USA	Country

The Silver Reef (Harrisburg, Leeds) mining district is in Washington County, about 15 mi northeast of St. George. Silver Reef was a large Ag-Cu producer from about 1875 until the collapse of the Ag price in 1893 and had continuing intermittent production until about 1980. In the 1950s, the district also produced a minor amount of U-V ore. Total district metal production at modern metal prices is estimated at $141 million. The largest Ag-Cu mines were the Leed-AS&R, Tecumseh-Harman, and California-Savage.
The district lies within the transition zone from the Basin and Range Province on the west to the Colorado Plateau on the east. Silver Reef is localized on the northeast-plunging nose of the large, Sevier-age, Virgin anticline. The Virgin anticline is an open, upright, symmetrical fold having a gentle plunge of about 10°–15° NE. The ore is primarily hosted in the Lower Jurassic Springdale Sandstone Member of the Moenave Formation. This sandstone is a thick-bedded, fine-grained, fluvial sandstone containing thin lenses of intraformational conglomerate with mudstone and siltstone rip-up clasts and poorly preserved carbonized plant remains (Biek and Rohrer, 2006).
The district has four major “reefs” or sandstone hogbacks; from west to east these are White, Buckeye, Butte, and East Reef. Buckeye Reef has been the most important, having yielded about 70% of the Ag produced. The average recovered grades from the district are approximately 577 ppm Ag and 1.3% Cu, but typical head grades are over 685 ppm Ag. The principal ore minerals are argentite, chalcocite, chlorargyrite, bornite, and native silver. The district is unique for the Ag-dominant character of its redbed-hosted Cu deposits (USGS Model 30b) with Ag accounting for very roughly 75% of the district’s production value. The district also has subordinate sandstone U-V production (USGS Model 30c). The best Cu-Ag mineralization is associated with the structurally complex, northwestern corner of the plunging anticlinal nose where the best host Springdale Sandstone is repeated three times by thrust faults. Individual orebodies are tabular, stratiform, stratabound, and average about 300 ft long, 100 ft wide, and less than 8 ft thick. The Ag-Cu ores are typically associated with carbon trash zones or thin, soft, shaly conglomerate interbeds (James and Newman, 1986). The most recognizable alteration is the bleaching of the host Springdale Sandstone resulting from the passage of reducing fluids, as evidenced by the gray-green rinds on the pink clay galls in the bleached sandstone. In addition to Ag-Cu, the ore is reportedly anomalous in As, Cl, Mo, Se, U, V, and Zn.

The mining district is unique; it is the only major mining district in the United States that produced silver ore from sandstone. From 1875 to 1972, the Silver Reef district produced 7.52 million ounces of silver, 665 ounces of gold, and 10.7 million pounds of copper. The 665 ounces of gold reported by Stowe is likely in error because district boundaries were not specific and gold production from other districts was added to the total. The district also produced 8400 pounds of uranium oxide from 1950 to 1957. Average grade of the silver ore hoisted was 20 to 50 ounces per ton.

John Kemple is credited for the discovery of silver ore at Silver Reef in 1866. His assayed ore samples were found to be rich in silver. Many did not believe the assay numbers because silver ore had never before been found in sandstone. Kemple did not trust his own assay results and set off for other mining camps in the West. He returned to Silver Reef for additional prospecting and in 1871 helped organize the Union mining district with L.D.S. church leaders and family heads from Harrisburg. All claims were later abandoned due to L.D.S. church concerns about the lawless aspect associated with mining and worries that farmers would leave their farms and orchards to become miners. Kemple again returned to Silver Reef and reorganized the district as the Harrisburg mining district in 1874. However, development of the district is credited to William Tecumseh Barbee after his 1875 silver ore discovery on Tecumseh Hill along a wagon road between Quail Creek and Leeds. A wheel from a wagon hauling wood to Leeds dislodged a piece of ore-bearing sandstone. The ore from this outcrop averaged 300 to 400 ounces of silver per ton. Barbee then promoted the district through glowing newspaper articles in Salt Lake City and Pioche, Nevada. Within the next two years, the new town of Silver Reef had reached a population of 1500. The town had all of the modern amenities, such as a post office, churches, schools, a bank, and a hospital. Most of the silver was produced during a five-year period between 1878 and 1882. Production began to decline in 1880, and by 1888 all of the major company-operated mines had closed. The rich, near-surface ores were mined out, ore grade decreased with depth, mining became more expensive, and ground water occupied the lower mine workings; all of these factors led to the closure of the district. Decline can also be attributed to the low price of silver on the international market. In 1877, silver was $1.20 per ounce and when mining ended in 1888, it was just $0.94. By 1903, Silver Reef was deserted.

The Silver Reef district received renewed interest in the 1950s for its uranium potential. In 1950, Western Gold and Uranium Corporation shipped at least 2500 pounds of uranium oxide. In 1979, 5M Corporation acquired the claims from the Western Gold and Uranium Corporation to process old mine tailings. This venture was short lived due to a decrease in silver prices. All that remains of the former town is a few old foundations and the Wells Fargo Building that is now a museum that documents the history of the mining district.