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Friday, October 16, 2009

Gold Mining in Tennessee


Almost all Tennessee's gold has come from placer deposits in Monroe County and from the copper ores of the Ducktown district in Polk County, both in the southeast corner of the State. Gold was discovered on Coker Creek, Monroe County, in 1827, and by 1854 a total of $46,023 worth of gold had been extracted from placers in this area, where sporadic small-scale operations continued from the close of the Civil War to about 1911. Total production from the Coker Creek area was about 9,000 ounces. Fissure veins, high terrace gravels, present stream gravels, and alluvial cones were mined. The vein deposits are too low grade to be of economic value. The search for gold in the early 1840's led to discoveries of copper ores at Ducktown, and mining of the rich chalcocite deposits began in 1847. By 1879 these ores were exhausted. Though there were large reserves of primary sulfide ore, the status of copper metallurgy and prices at that time made further mining unprofitable. After 1890 new roasting techniques were developed; the mines were reopened and were active through 1959. Gold ores, as such, were not mined in the Ducktown district, but small amounts of gold and silver were recovered from the sulfide ores after 1904. Although early records are incomplete and inaccurate, the best available data indicate that Tennessee's total gold production from 1831 through 1959 was about 23,800 ounces, of which 14,872 ounces was recovered from the Ducktown ores. The country rocks in the Ducktown district consist of graywacke, conglomerate, mica schist, slate, staurolite schist, and garnet schist, all units of the Great Smoky Group, of late Precambrian age. These are cut by several gabbro dikes. The rocks have been intricately folded, but the major pattern consists of three northeastward-plunging anticlines on which are superimposed numerous drag folds. Three fault systems, some preore and others postore, cut the rocks. The ore deposits are tabular or lens-shaped replacement bodies in limestone in the mica schist, which has been complexly folded and faulted . Ross (1935, p. 40-43, 97-101), on the other hand, believed the deposits to be multistage hydrothermal vein depos'.ts. The ore is of three types: surficial gossan, rich in hydrous iron oxides; sec- ondary sulfide ore, just below the water table; and the primary sulfide ore. The primary minerals are pyrrhotite, chalcopyrite, pyrite, sphalerite and minor amounts of galena, bornite, magnetite and arsenopyrite. Gangue minerals in the primary ore are actinolite, tremolite, garnet and some zoisite, quartz, calcite, and dolomite. In the secondary ore, chalcocite is the most abundant ore mineral. Covellite, marcasite, and numerous copper sulfates are sparse, and small amounts of gold and silver occur in the primary and secondary sulfide ores.

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