THE SAGA OF COLORADO GOLD
was claimed, and Pickens could not obtain a lease.
Pickens told no one of his find for 18 long years. Finally, in 1926, he managed to lease the property and begin mining. His long wait was well worth it. Although the vein was small, the average ore grade was 28 troy ounces of gold per ton, but the vein’s narrow center section graded 230 troy ounces per ton. In just three years of small-scale mining, Pickens recovered a half-million dollars in gold.
The dollar values for gold mentioned thus far are based on a gold price of $20.67 per troy ounce. In the early 1930s, the United States and most other nations abandoned the gold monetary standard and revalued the metal. The new price, fixed at $35 per troy ounce in 1934, stimulated gold mining in Colorado and worldwide. The increased gold price coincided with the height of the Great Depression. With jobs hard to find, rusted gold pans and old sluices were put to work again on all of Colorado’s gold-bearing creeks and rivers. Many nearly abandoned gold-mining districts came back to life as miners increased production at operating gold mines, reopened many long-closed mines, and constructed new bucket-line dredges.
Gold mining even resumed along the South Platte River in Denver. To provide an income opportunity for the jobless, the city of Denver conducted free “goldmining schools” in which experienced placer miners taught the largely forgotten arts of panning and sluicing. Thousands of out-of-work “students” participated, and the schools enabled their many “graduates” to pan or sluice a few dollars worth of gold every day—enough to put food on their tables. The renewed placer-mining activity also showed that the old-timers hadn’t found all the big nuggets. In 1937, high on Pennsylvania
Mountain near Fairplay, miners recovered an 11.95 troy ounce nugget. Named the “Penn Hill nugget,” it is the largest-known Colorado placer nugget ever found.
After World War II, inflation quickly caught up with $35 gold, and most of Colorado’s gold deposits were no longer worth mining. But the future of gold mining, not only in Colorado but worldwide, was already on the drawing boards in Cripple Creek. The Golden Cycle Corporation, the only surviving Cripple Creek mining company left from the boom days, constructed the Carlton Mill in 1950 to conventionally process the district’s few remaining ores. Like many districts, Cripple Creek had enormous quantities of gold mineralization left in the ground that was far too low in grade to mine profitably.
When a United States Bureau of Mines research team needed a place to test an experimental cyanidationrecovery process, Golden Cycle generously donated an unused corner of its Carlton Mill. Cyanidation, which uses cyanide solutions to dissolve metallic gold from ores, was nothing new. It had been introduced in the 1890s, but its use was limited because the only way to recover the dissolved gold was through costly and inefficient precipitation with powdered zinc. In 1951, the Bureau of Mines researchers at the Carlton Mill developed an inexpensive process to recover the dissolved gold from cyanide solutions by adsorption onto particles of activated charcoal and chemically desorp the gold in metallic form. By making mass cyanide leaching of very low-grade gold ores profitable, this process would revolutionize gold mining.
By the 1970s, when gold had become a free-market commodity, and its price had soared, the cyanidationcharcoal-adsorption approach was adopted worldwide.