Plum Mine, Storey County, Nevada, USAi

Regional Level Types
Plum Mine	Mine
Storey County	County
Nevada	State
USA	Country

Structure: block faulting; Silver City Fault

Commodity: Ore Materials: free gold, native silver, electrum, pyrite, argentite Gangue Materials: calcite, ankerite, manganese oxides, quartz

Deposit: Goldsprings' current mining operations are located on the historic Silver City lode vein deposits. Concentrated gold and silver are contained within a three-dimensional interlocking quartz stockwork and in manganiferous-quartz-calcite veins. Outside of the manganiferous zone, significant gold and/or silver values generally conform to the geometry of the Silver City lode. Gold mineralization is contained within breccias, as is typical of Silver City lode deposits. The hanging wall and mineralized rock are younger, Tertiary volcanics, while footwall is composed of Mesozoic units. Late pyrite (post-mineral) occurs abundantly in gouge and wallrocks. Locally, Tertiary-aged rocks are also found in the footwall. Ore production was confined to shallow depths, (less than 300 ft).

Deposit type: Epithermal vein, Comstock

Development: The Silver City branch of the Comstock Lode south of Virginia City has seen many generations of mining and exploration activity for precious metals over the years. It was estimated that between 1871 and 1940, the Silver City lode vein system produced about 6 tonnes of gold and 236 tonnes of silver from 611,000 metric tonnes of ore. The area continued to attract precious metals exploration activity in the 1960s, and in the 1970s-1980s, Houston Oil and Minerals Corporation operated a gold-silver mine on part of the current Goldspring property. Houston closed down operations in the 1980s but the Lucerne Pit area has continued to be worked intermittently since first discovered. Rea Gold did exploratory drilling in the early 1990s and planned to mine the smaller, higher grade Lucerne Starter pit followed by mining of the larger Lucerne Main pit. The operations were called the South Comstock Joint Venture (listed in Lyon County, but workings extend just over the county line to the north in Storey County) and produced 6,936 ounces of gold and 72,139 ounces of silver from 124,000 tons of ore in 1993-1994. Plum Mining Company was active in the district from the mid-1990s to 2004, and GoldSpring, Inc. was also active in the area, with a dump reworking project on the Comstock lode dumps to the north and placer claim operations three miles to the south. BMR also operated the South Comstock Joint Venture in the late 1990s, with property extending across the county line to the south into Lyon County. In 2004, GoldSpring, Inc. purchased Plum Mining Company, LLC, owner of the Billie the Kid open-pit mine, which was reported to contain substantial drill-proven reserves. The pit was on patented land and fully permitted for operation. The average drill proven grade was 0.074 opt Au and 0.32 opt Ag. Goldspring began operating the Billie the Kid (Plum) Mine in 2004. It is just 500 meters south west of the Lucerne open pit, where additional reserves remain. GoldSpring, Inc. set up a Direct Electrowinning (EMEW) gold and silver metals recovery plant at the Plum Mining Cyanide heap leach facility to enable recovery capacity to exceed 100 oz gold and 200 oz silver per day. As of end of 2004, 100,000 tons of ore from Billie the Kid open pit have been mined and loaded on the heap leach pad since January 2004 and regular shipments of gold-silver dore have been made to Johnson Matthey Refinery in Salt Lake City since June 2004. Approximate production as of September 20, 2004 was 1,500 ounces of gold and 6,500 ounces of silver. Annual production estimates were projected to be 25,000 ounces of gold and 125,000 ounces of silver, at a projected cash cost per ounce of gold production of $190. The project life estimate is 5 to 7 years.

Geology: Gold mineralization is contained within breccias, as is typical of Silver City lode deposits. The hanging wall and mineralized rock are younger, Tertiary volcanics, while footwall is composed of Mesozoic units. Locally, Tertiary-aged rocks are also found in the footwall.

Ore(s): Silver City Fault zone

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Link to USGS MRDS:	10310466

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