Gold Mines and Mining
GOLD MINES AND MINING
GOLD MINES AND MINING. Gold mining in the United States began in the foothills of the Appalachian Mountains in North Carolina following the chance discovery of a nugget of free gold in 1799. Limited but continuous activity there and in Georgia after the opening of gold deposits in 1828–1829 resulted in the production of an estimated $24.5 million in gold in the years before 1848. This record was completely and dramatically eclipsed in the goldfields of California after the discovery of gold at Coloma by James Wilson Marshall in January 1848. The gold flakes that Marshall found in the run at John Sutter's mill were not the first gold found in California; Mexicans had worked placer deposits near Los Angeles since 1842. But the Coloma strike touched off a mass migration to the goldfields of the newly acquired territory. The first decade of California mining, 1848–1858, saw some $550 million in gold extracted.
The early California mines were placer deposits of free, or pure, gold mixed with sand and gravel. The mining pan became the basic tool of the placer miner. He recovered the gold by agitating water and debris in the pan; the gold, being heavier than the sand or gravel, settled to the bottom of the pan. Refinements such as the rocker, sluice, tom, dredge, and hydraulic nozzle are all
devices employing the same principle as the pan—that of washing the gold-bearing debris with water. The only chemical process used was mercury-gold amalgamation. Mercury and gold have a natural affinity for each other and, when brought into contact, form an amalgam. Separated from other debris, the amalgam can be heated, driving the mercury off as a vapor, leaving a residue of free gold.
In time, as the easily worked California placer deposits began to be exhausted, interest turned to lode mining, the mining of free gold in streaks or veins embedded in quartz or rock. Lode mining called for relatively complicated and expensive methods of crushing the ore, and early tools such as the Spanish arrastre were soon replaced by steam-powered stamp mills. Washing and amalgamation followed the pulverizing of the ore to recover the gold. The Empire and the North Star mines at Grass Valley were California's most successful lode mines.
The California gold mining initiated a continuing series of gold strikes in the trans-Mississippi West, and the experiences of California miners proved valuable lessons in the new camps. Mining laws and mining methods, with many ingredients borrowed from Spanish mining via Mexico, were exported from California to the new fields. In 1859 the Comstock lode in Nevada, with its rich gold and silver ores, gave rise to the boomtown of Virginia City. The year before, small placer deposits had been found near Cherry Creek in what was to become Colorado, touching off the Pike's Peak rush in the spring of 1859. In the following decade camps were opened in Idaho and Montana, and the Black Hills region of South Dakota experienced the same pattern in the years after 1875. The Alaska fields were first mined in the 1880s, with later and richer discoveries in 1898 near Cape Nome and in 1902–1903 in the Fairbanks region. Goldfield and Tonopah provided Nevada with a second rush in 1903–1905.
Most of the gold discovered was free gold, and mechanical methods of separation were sufficient for recovery. Even so, as mines were extended farther and deeper, more extensive methods were required to extract the ore. Fortunately, through borrowings from abroad and on-site innovations, technology kept pace with need. The Com-stock operations in Nevada in 1865–1875 were especially noted for application and adaptation of new techniques. The compressed-air drill and the diamond-studded rotary drill were borrowed from France; the new explosives nitroglycerine and dynamite, used for blasting, were introduced from Sweden; and A. S. Hallidie of San Francisco perfected the flat, woven-wire cable used in hoists.
Where gold is found in combination with other elements, the problems of extraction are more complex. Advances in metallurgical chemistry were necessary before such ores could be profitably worked. One of the first successful chemical processes for separation of refractory ores was the cyanide process, perfected in 1887. This process involved the placing of finely crushed gold ores in a solution of potassium cyanide, where the gold cyanide that formed could be removed either with zinc or by electrolysis. This process and others such as chlorination and oil-flotation were available when the Cripple Creek fields of Colorado were opened in 1891. The nation's richest mining district developed from the telluride ores of Cripple Creek; the two biggest producers, the Portland and the Independence mines, accounted for more than $100 million in gold in the years after 1891. The new chemical processes also made possible the reworking of older mines to recover gold from low-grade ores and the development of new areas in which low-grade ores existed, such as the San Juan region of Colorado, with its Camp Bird, Liberty-Bell, and Smuggler-Union mines.
Mine production reached its highest levels in the decade 1905–1915, when an annual average of 4,513,480 fine ounces of gold was produced in the United States. After World War I gold mining decreased markedly. High-grade ores had been exhausted, and the costs of extraction and refining had increased. After 1920 the Homestake mine at Lead made South Dakota the leading gold-producing state. In 1970 three states (South Dakota, Nevada, and Utah) mined 84 percent of the 1,743,000 fine ounces of gold produced in the United States.
Gudde, Erwin Gustav. California Gold Camps: A Geographical and Historical Dictionary of Camps, Towns, and Localities Where Gold Was Found and Mined, Wayside Stations and Trading Centers. Berkeley: University of California Press, 1975.
Paul, Rodman Wilson. The California Gold Discovery: Sources, Documents, Accounts, and Memoirs Relating to the Discovery of Gold at Sutter's Mill. Georgetown, Calif.: Talisman Press, 1966.