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Gold mining in Colorado, a state of the United States, has been an industry since 1858, and played a key role in the establishment of the state of Colorado. Explorer Zebulon Pike heard a report of gold in South Park, present-day Park County, Colorado in 1807.〔A. H. Koschman and M. H. Bergendahl (1968) ''Principal gold-Producing Districts of the United States'', US Geological Survey, Professional Paper 610, p.143.〕 Gold discoveries in Colorado began around Denver, traced the placer gold to its source in the mountains west of Denver, then followed the Colorado Mineral Belt in a southwest direction across the state to its terminus in the San Juan Mountains. The Cripple Creek district, far from the mineral belt, was one of the last gold districts to be discovered. ==Denver-area placers== On June 22, 1850, a wagon train bound for California crossed the South Platte River just north of the confluence with Clear Creek, and followed Clear Creek west for six miles. Lewis Ralston dipped his gold pan in a stream flowing into Clear Creek, and found almost $5 in gold (about a quarter of a troy ounce) in his first pan. John Lowery Brown, who kept a diary of the party's journey from Georgia to California, wrote on that day: "Lay bye. Gold found." In a notation above the entry, he wrote, "We called this Ralston's Creek because a man of that name found gold here." Ralston continued on to California, but returned to 'Ralston's Creek' with the Green Russell party eight years later. Members of this party founded Auraria (later absorbed into Denver City) in 1858 and touched off the gold rush to the Rockies. The confluence of Clear Creek and Ralston Creek, the site of Colorado's first gold discovery is now in Arvada, Colorado.〔Voynick, S.M., 1992, Colorado Gold, Missoula: Mountain Press Publishing Company, ISBN 0878424555〕 A gold discovery in 1858 in the vicinity of present-day Denver sparked the Pike's Peak Gold Rush. In 1858, prospectors focused on the placers east of the mountains in the sands of Cherry Creek, Clear Creek, and the South Platte River. However, the placer deposits on the plains were small, and when the first rich discoveries were made in early 1859 in the mountains farther west, the miners abandoned the placers around Denver. Although the economic portions of the gold placers around Denver were quickly exhausted, producers of construction aggregate in the area sometimes recover small amounts of gold from their sand and gravel washing. The plains counties of Adams, Arapahoe, Douglas, Denver, Elbert and Jefferson are each credited with having produced small amounts of gold.〔Ben H. Parker Jr., Gold placers of Colorado, book 1, Quarterly of the Colorado School of Mines, v.69, n.3, July 1974, p.26.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gold mining in Colorado」の詳細全文を読む スポンサード リンク
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