Abstract

The Silver Reef mining district consists of four “reefs” on the northeast-plunging nose of the Virgin anticline: White, Buckeye, and Butte Reefs are on the anticline’s northwest flank, whereas East Reef is on the anticline’s east flank. The district is noted for its uncommon occurrence of ore-grade silver chloride in sandstone, unaccompanied by obvious alteration or, with the exception of copper, substantial base-metal ores. The ore horizons are contained in the Springdale Sandstone Member of the Moenave Formation, which is repeated by thrust faults on the anticline’s northwest flank.

High-grade silver chloride float was first discovered near Harrisburg in 1866, and in-situ mineralization was found in 1868, but it was not until 1876 that the silver rush was underway in earnest. The principal mining activity in the district lasted only through 1888, with lessee operations through 1909, after which major mining essentially ceased. Prior to 1910, the district produced over 7 million ounces of silver, nearly 70 percent of which came from the prolific Buckeye Reef. The mines were shallow, less than 350 feet deep, and most ore bodies were lens shaped, averaging 200 to 300 feet in length along strike by about half as wide and up to about 20 feet thick. The ore averaged 20 to 50 ounces silver per ton, but varied from only a few ounces to about 500 ounces per ton. Sporadic production between 1949 and 1968 yielded about 10 ounces of gold, 165,000 ounces of silver, 34 short tons of copper, and at least 2,500 pounds of uranium oxide. A leach-pad operation established between White and Buckeye Reefs to process tailings opened in 1979, but this venture closed with the collapse of silver prices. The district continues to be periodically explored for silver.

Reclamation of the White, Buckeye, and Butte Reefs, completed during 1996 to 1997, involved 465 mine closures at a cost of $469,000; it was the largest single mine closure project for the Utah Division of Oil, Gas and Mining, Abandoned Mine Reclamation Program to date. Reclamation of 184 mine openings at the East Reef area was completed in 2000 at a cost of $170,000. Reclamation of the Silver Reef mining district was complicated by the fact that (1) the district is considered a “rural historic landscape” eligible for the National Register of Historic Places; (2) it is home to one of the state’s largest Corynorhinus townsendii (Townsend’s big-eared bat) maternity colonies and has numerous roosts for other bat species; and (3) because in the past three decades, the adjacent town of Silver Reef has experienced a second real estate and population boom and is now an upscale residential community.