Leadville Mining District, Lake County, Colorado, USAi

Regional Level Types
Leadville Mining District	Mining District
Lake County	County
Colorado	State
USA	Country

A former Ag-Zn-Au-Pb-Cu-Mn-Fe-S-Bi-Cd-V-W mining district. The district extends from Leadville East to the crest of the Mosquito Range and from Canterbury Hill and Prospect Mountain in the North to Empire Gulch in the South. It includes about 30 square miles, mostly in T9S, R79 & 80W. The most intensely mineralized area lies immediately East of Leadville and covers about 8 square miles. Operated during the period 1860 to 1999. Coordinates provided by the USGS MRDS database are to the approximate center of the district.

At today's metal prices (2006), Ag, Zn, Au, & Pb are the main products of the district; Cu is a byproduct. Manganiferous iron ore was used in steelmaking; iron-silver and iron-manganese-silver ores were produced for smelter flux. Bi & Cd were recovered as byproducts of smelting. Pyrite was used to make sulfuric acid. Tungsten minerals (in one ore body) and vanadium minerals are reported but have not been recovered.

Mineralization is comprised of replacement deposits (Deposits data: Model code 72; USGS model code 19a; Deposit model name: Polymetallic replacement; Mark3 model number 47;; Model code 56; USGS model code 17a; Deposit model name: Placer Au;; Model code 224; USGS model code 32a; BC deposit profile E12; Deposit model name: Mississippi Valley, S.E. Missouri Pb-Zn; Mark3 model number 42) hosted in rocks of the Curtis Formation (dolomite). The host rocks include Proterozoic Sawatch Quartzite; Cambrian Peerless Shale; Cambrian Manitou Dolomite; Ordovician Parting Sandstone; Devonian Dyer Dolomite; Devonian Gilman Sandstone; Late Devonian Leadville Dolomite; Mississippian Belden Formation black shale; Pennsylvanian Minturn Formation arkose; Pennsylvanian porphyry (Pando, Lincoln, Evans Gulch, Sacramento, Johnson Gulch, rhyolite, and fragmental porphyries). Associated rocks include Tertiary St. Kevin Granite. Gangue contains manganoan siderite (manganosiderite). Local alteration includes silicification & sericitization. Local rocks include Laramide intrusive rocks.

Major minerals in each of four types of ore bodies are listed: (1) hypogene oxide-silicate ore, (2) hypogene sulfide veins and stockworks, (3) blanket or manto replacement ore, and (4) oxidized or supergene ore.

Granitic and metamorphic basement rocks are overlain by 500 feet of east-dipping marine Paleozoic sedimentary rocks, cut by numerous faults, and intruded by many Tertiary igneous rocks. Five types of ore bodies are (1) hypogene oxide-silicate ore, (2) hypogene sulfide veins and stockworks, (3) blanket or manto replacement ore, (4) oxidized or supergene ore, and (5) placer deposits.

Local geologic structures include numerous faults of several periods.

After 140 years of nearly continuous mining activity, the Leadville district ranks among the most productive areas for base and precious metals in the U.S. First, gold placer deposits, then lode gold deposits were worked, from 1860 to 1875; oxidized silver-lead ores were dominant from 1876 to 1902; then oxidized zinc ores were worked from 1902 to 1923; finally, mixed sulfide base- and precious-metal ores were mined from 1924 almost continuously until 1999.

Production information: An estimate of total metal production, based on published reports and the reporter's estimate of recent production, includes 3,250,000 ounces of Au, 270,000,000 ounces of Ag, 53,000 tons of Cu, 1,200,000 tons of Pb, and 1,235,000 tons of Zn. Nearly 29 million tons of ore were mined. Almost 1,000,000 tons of manganiferous iron ore and 2,900,000 tons of iron-silver and iron-manganese-silver ore, plus an unknown quantity of pyrite, were produced.

For the 1860-1999 cumulative production listed in the previous comment, assuming the amounts are metric tons, at 2010 prices, the commodity importance order and dollar value in millions is: Ag $4.9 Au $3.7 Zn $3.0 Pb $2.6 Cu $0.4 For the 1860-1963 cumulative production, Tweto, 1968, lists the relative economic importance as follows: 37% Ag; 22% Zn; 21% Pb; 13% Au; 3% Cu; 4% other including Bi and Mg.

Production statistics data: Year: 1999 (period 1860-1999): Ore mined: 29,000,000 metric tons.

Production history details: Primary recovery: Ag: 8,400 metric tons; Zn: 1,235,000 metric tons; Au: 101 metric tons; Pb: 1,200,000 metric tons; and, Secondary recovery: Cu: 53,000 metric tons.

Reserve resource information: Low-grade manganese resources may total 2,000,000 tons of oxidized ore, containing 10% to 35% Mn, plus 2,000,000 tons of primary (manganosiderite) ore, containing 14 to 20% Mn. (Hedges, J.H., 1940).