Park City Mining District, Summit County, Utah, USAi

Regional Level Types
Park City Mining District	City
Summit County	County
Utah	State
USA	Country

The Park City (Uintah, Snake Creek) mining district lies in the Wasatch Range of Summit and Wasatch Counties about 22 mi east of Salt Lake City. The district is essentially tied with the greater Tintic district for the second largest mining district in the state in terms of total metal production value. The principal metals produced are Ag, Pb, Au, and Zn, in decreasing order of importance. Park City is the second largest Pb, Zn, and Ag producer in the state. Total district metal production at modern metal prices is estimated at $10 billion. The largest producers in the district are the Daly West, Mayflower, Ontario, Park Utah, and Silver King Coalition underground mines (John, 2006).
The Park City district is part of the Bingham–Park City mineral belt in the Middle Rocky Mountain province. The district is underlain by a sequence of Mississippian- to Triassic-age interbedded carbonate rocks, sandstone, and shale folded along the gentle, north-plunging, open, upright, asymmetrical, Park City anticline and cut by gently west-dipping thrust faults. These older structures are cut by a series of east-northeast-trending, steeply dipping, normal faults which extend eastward from the Clayton Peak stock across the Park City anticline. A number of diorite to granodiorite porphyry stocks (34–33 Ma) intrude the south end of the anticline (John, 2006).
The vast majority of the Park City district’s production is from sedimentary rock-hosted vein and replacement ores. These ores primarily occur along the east-northeast-trending faults producing veins in the relatively non-reactive Pennsylvanian- Permian Weber Sandstone in the core of the anticline and mantos in the adjoining favorable limestones. The most important ore host is the Jenny horizon, about 100 ft above the base of the Permian Park City Group and just above the Weber Sandstone. Only the Mayflower veins in the southeastern end of the district are important intrusive-hosted (granodiorite) ores. The Mayflower veins were productive over a vertical distance of nearly 3300 ft and had the highest Cu and Au grades in the district. Bromfield (1989) maps a central zone of hydrothermal biotite surrounded by quartz-sericite-pyrite at the surface near the Mayflower mine. Pebble dikes and a breccia pipe were also reported from the Ontario and Mayflower mines in the southern section of the district.
The Park City district appears to be zoned from intrusive-hosted, enargite-bearing Cu-Au-rich ores near the Mayflower in the southeast, through Ag-Pb-Zn replacement ores in the central and western parts of the district (USGS Model 19A), to distal Ag- dominant ores at the Park City Consolidated mine in the northeast near Deer Valley (John, 2006).

From 1875 to 1982, the Park City mines produced 16.7 million tons of ore recovering 1.45 million ounces of gold, 253 million ounces of silver, 2.7 billion pounds of lead, 1.5 billion pounds of zinc, and 129 million pounds of copper. With these totals, the Park City mining district is the third-leading non-ferrous metal producer in the state.

The Park City district comprises three former districts (Uinta, Snake Creek, and Blue Ledge), and who made the first mineral discovery in the district is unknown. The first claims recorded were the Young America in 1868 and the Green Monster in 1869. A short time later Rufus Walker located the Walker and Webster claim and exploration began in earnest. With an increasing number of discoveries, the Uinta district was organized in 1869. The Snake Creek and Blue Ledge districts were established in the spring of 1870. The first recorded production of lead-silver ore in the Park City district was from the Flagstaff mine in 1871. The discovery of the Ontario vein in 1872 by Rector Steen, John Kain, and Gus McDowell catapulted the district into prominence. The vein was exposed on the surface as a knob, protruding two inches out of the ground. The first ore mined from this property averaged $200 dollars of silver per ton. These prospectors subsequently sold the mineral rights to George Hearst and partners in 1872 for the amount of $27,000.

In 1881, a Cornish pump was installed in the Ontario mine to pump out ground water. The pump had a wheel that was 30 feet in diameter, weighed 70 tons, and pumped 2560 gallons of water per minute. As the mine became deeper, the Cornish pump became inefficient at handling the excessive amount of water.

In 1888, excavation work began on the 3-mile long Ontario drain tunnel to eliminate water from the lower workings of the mine. The tunnel took six years to complete at a cost of $400,000. The tunnel linked up with the 1500-foot level of the mine and was capable of draining up to 13,000 gallons of water per minute. In its lifetime, the Ontario produced ore worth over $50 million, making this property one of the best land purchases of all time. The Ontario was mined from the surface to a depth of 2000 feet, and was highly productive in the upper 1500 feet. The ore averaged 21 ounces of silver per ton and approximately 3 percent lead. Other major mines in the district include the Daly West, Daly-Judge, Park-Utah, Mayflower, Park City Consolidated, and Silver King.

During World War II, metal production from the mines decreased dramatically. Many of the skilled workers were sent to the war and government restrictions prevented the search for new mineral deposits.

In 1958, the United Park City Mines, the last surviving mining company in Park City, looked closely at their property for other ways to generate money. Because the silver market was on the downside, the company turned to skiing with assistance from the federal government. With a federal loan of $1.2 million and land ownership of the surface rights to approximately 10,000 acres of mountainside, the mining company created Park City’s first ski resort. In 1963, Treasure Mountain, now known as the Park City Mountain Resort, opened to the public.

Mining continued at the Mayflower mine, where the ore contained higher gold and copper values per ton than any of the other mines in the district. In 1966, the Mayflower mine ranked sixth in gold production in the United States, and in 1967 the mine produced 72,000 ounces of gold. The Mayflower mine closed in 1972.

After a period of inactivity, mining resumed at the Ontario mine in the spring of 1975. For three years, the Ontario mine produced ore until its closure in 1978. The Noranda Mining Company leased the mine from 1979 to 1982. In 1995, the Ontario mine was opened for the first time to tourists. Called the Park City Mine Adventure, tourists could descend 1500 feet underground to view the Cornish pump, minerals, and old mine workings. Unfortunately, this latest venture lasted only several years.