By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Discussions of these two counties, which adjoin each other along the east slope of the Wasatch Range, are combined because the major mining district in the area, the Park City district, straddles the boundary. Gold production data for the counties were not found, but as the Park City district is the only mining center of any consequence in either county, the district's production of approximately 790,000 ounces through 1959 is assumed to be equivalent to that of both counties.
PARK CITY DISTRICT
The Park City district, about 25 miles southeast of Salt Lake City, encompasses the Uinta district in the southwest corner of Summit County and the Snake Creek and Blue Ledge districts in the northwest corner of Wasatch County.
Though silver and lead are the chief commodities, considerable gold, copper, and zinc are also mined. The 790,000 ounces of gold produced through 1959 makes Park City the fourth largest gold district in Utah.
After the discovery of ore in the middle 1860's in the Little Cottonwood and other districts on the west slope of the Wasatch Range, prospectors crossed to the east slope of the range and discovered lead-silver ore in the Park City district in about 1869. The first shipment of ore was made in 1870 or 1871 (Boutwell, 1912, p. 19). Important discoveries of lead-silver ore were made in rapid succession and resulted in the organization of the Uinta district in Summit County in 1869 and in the Snake Creek and Blue Ledge districts in Wasatch County in 1870. In 1872, about 2 years after the first locations were made, the famous Ontario vein was discovered. Its bonanza ore bodies stimulated interest in the new area and gave Park City early prominence in the turbulent mining industry. Prospecting in the western part of the district led to discovery of rich lead-silver replacement deposits on Treasure Hill and, in 1892, to the opening of extensive replacement deposits at the Silver King site.
Because of the high content of the ores, the prosperity of the district fluctuated with the price of silver; the decline in price in the 1890's, especially in 1893, caused temporary intermittent production or closure in some mines. However, the lower prices in 1893 stimulated development of more economical methods of mining and reduction and more effective recovery methods, and large concentrating mills were erected to treat larger volumes of low-grade ores. In 1901 new discoveries of rich smelting ore were made and Park City production increased abruptly. After 1905 zinc became an important product. Recent activity in the district is toward the consolidation of the older properties and deeper exploration for bedded replacement ore bodies; the rich oxidized surface ores have long been depleted. The two major operators in the area are United Park City Mining Co. and New Park Mining Co. (C. L. Wilson, in Williams, 1959, p. 182).
Predominant bedrock in the district is a section of sedimentary formations that are folded, faulted, and intruded by igneous rocks and are covered locally by volcanic rocks.
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