Either Ore, Neither More: Gold and Iron in Boom and Decline

Underlying most histories of mining are the physical properties of the Earth. The material circumstances under which desirable minerals are found posed challenging preconditions to those historical actors who wanted to extract them. The Dictionary of Mining, Mineral, and Related Terms calls "ore" the "naturally occurring material from which a mineral or minerals of economic value can be extracted profitably."¹ A mine's "ore," then, can be gained or lost without putting a shovel in the ground. A technological breakthrough might make extraction of particular minerals from certain earthy material economically viable, expanding reserves of now-profitable "ore." Global markets or government policy might raise or lower commodity prices, enlarging or shrinking quantities of ore proportionately.

Authors Clark C. Spence and Jeffrey T. Manuel tell histories of mining people and mined places that both acknowledge, sometimes implicitly, this fundamental equation. The gold, or the iron, was almost always there (in a geological sense), but could miners gather it cost effectively? Was there a market for the product? Could capital return investment? Would jobs be created? What would remain once the "ore" was gone? Was it worthwhile to try to mine. Spence, Emeritus Professor at the University of Illinois, has made the history of mining one of the major research concentrations of his lengthy and distinguished career.² Here, he recounts the history of gold-dredging operations in Idaho, with a level of detail unlikely to ever be surpassed. Dredging operations focused on placer claims: deposits where particles of valuable material, especially gold, were mixed with sand or gravel instead of being trapped in a rock matrix, as in hard-rock mining. In principle, to operate any kind of placer mine, a miner would dig up the gold-bearing dirt, then use water and gravity to winnow the heavier gold particles from lighter material. Placer-mining technology consisted of devices to help miners dig up the placer deposits, typically located on or near the surface; devices to bring water to the mine site; and devices to help agitate the dirt/gold mixture with water, then catch the freed gold particles. (Such devices ranged from the humble gold pan to rockers, long toms, and sluices).

Across the West in the second half of the nineteenth century, placer miners were quick to set up operations in a promising area and just as quick to abandon them. Many of these worked-out placer districts still contained gold, of course, just not "ore." At the turn of the twentieth century, new mining machines called dredges promised a technological fix to revive old placer claims. A dredge was a mass-production placer mining machine, with digging, sorting, washing, and tailings-removal machinery integrated together on a floating hull. It processed large volumes of pay dirt and was capable of making a profit on ground whose gold content was too lean (or too deeply located) to work with earlier methods. In use in New Zealand by the early 1880s, the first U.S. gold dredge began operations at Bannack, Montana, in 1895. The last years of the nineteenth and first decades of the twentieth century saw a period of experimentation and adaptation in U.S. gold dredging that yielded a family of machines—the California-type dredges—that were more durable, larger, and more efficient than their predecessors. The capabilities of these new machines made them the key technology in a renewal of placer mining on a massive scale prior to World War II. The greatest U.S. production came from California, Alaska, Montana, and Idaho.

Spence's A History of Gold Dredging in Idaho consists of seventeen chapters plus an introduction and an epilogue. The introduction, epilogue, and overview chapters (the latter confusingly located at the end...