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March 2008
Introduction to Bodie’s Mineralogy
By
Fortune seekers who rushed west in 1849 expected to find gold quickly. Employing methods known as “placer mining,” they dug nuggets and gold dust from the banks of California’s rivers. Gold is also encased in rocky formations below ground where geological events deposited it millions of years ago. While placer miners washed gravel on the surface, other miners drove tunnels and sunk mineshafts deep into the earth to reach gold-bearing minerals. Blasting through solid rock, they sought particles of gold that were often miniscule and invisible to the naked eye. Because subterranean gold deposits usually lie in quartz, the underground mining of gold was called “quartz mining.”(1) At Mariposa County in 1849, miners found gold-laden quartz and began California’s first quartz mine.
Subsequent discoveries of gold in rock other than quartz failed to affect the term, and “quartz mining” expanded to mean underground gold mining regardless of the chemical composition of the surrounding rock. After silver was discovered in quartz on the Comstock in 1859, “quartz mining” included the underground mining of silver, as well as gold. By the time Bodie boomed twenty years later, “quartz” implied much more than the conventional mineral, defined in 1881 as “any hard gold or silver ore, as distinguished from gravel or earth.” (Raymond 1881, 167) Recent descriptive terms, such as “lode” or “hard rock” mining, have been applied to underground gold and silver mining, but the term employed during the nineteenth century was “quartz mining.”
Driving tunnels and sinking shafts were expensive endeavors that could not be sustained for long by individuals. Most prospectors sold their claims to big-city capitalists with the ability to organize companies and finance mining by selling stock. Although the odds were astronomical against striking it rich, people across the country eagerly invested. Speculating in western gold and silver mines became a popular pastime—something akin to playing today’s lotteries. The spirited reception of western mining stocks encouraged a proliferation of unregulated companies, many of which cheated investors and scandalously misused their money. Widespread corruption discredited the industry, leading the wary public to identify “quartz mining” with “swindle.”
Scores of mining companies at Bodie sold stock, hired miners, and purchased machinery to exploit quartz deposits that investors hoped would yield enough mineral wealth to return big profits. Reaching the ore, however, involved considerable effort and expense. Surrounding Bodie’s quartz deposits was a yellowish volcanic rock that mining men called “porphyry,” known to geologists as “andesite.” Using drills and dynamite, miners burrowed through it, blasting away tons of worthless rock that they removed and dumped at mine entrances.
Bodie is famed for gold, which represented most of the value in its bullion. But, along with the gold came silver. For every dollar produced from Bodie’s ore during the early 1880s, about 70 cents was gold, 30 cents silver. Silver, however, was far less valuable than gold. An average 100-pound bar of the district’s bullion contained about 73 pounds of silver, but only 27 pounds of gold. This high silver content made Bodie’s bullion very pale in color with little, if any, discernible golden hue.(2)
Most of the silver in Bodie’s ore came from two sources. First was the gold itself. Gold is rarely pure in nature and is almost always mixed, or alloyed, with silver and sometimes other metals, such as lead, iron, or copper. Gold sometimes contains enough silver to significantly reduce its value, as was noted by early Nevada placer miners at Washoe, who grew concerned when their gold flakes and nuggets were lighter in color than the California gold to which they were accustomed. In his history of the Comstock Lode, Dan De Quille explained the unwelcome characteristics: “The gold dug in the placer-mines of California is worth from $16 to $19 per ounce, whereas the gold taken from the croppings of the Comstock was worth no more than $11 or $12 per ounce.” (De Quille 1876, 24) The concept that a piece of gold can be diluted in value was recognized by Grant Smith, who recalled Bodie: “All of the gold in the district was heavily alloyed with silver, and was rarely worth more than $12 per ounce. In some of the shallow placer diggings, at the south end of the ridge, the gold was worth only from $3 to $8 per ounce.” (Smith 1925, 76) In discussing mining at Bodie, the term “gold” assumes a certain silver content.
The second major source of silver at Bodie was rock that surrounded the particles of gold. Discoloring the normally white quartz were chemical compounds of silver combined with other elements, notably sulfur. These minerals were known as “sulphurets,” an old-time mining term for any gold- or silver-bearing ore possessing sulfides. Sulphurets at Bodie included argentite (known on the Comstock as “blasted blue stuff”), chalcopyrite, galena, pyrargyrite (a crimson mineral called “ruby silver”), pyrite (a brassy colored mineral), stephanite, and tetrahedrite. Defying ordinary gold mill processes, sulphurets required specialized treatment to extract their silver. Very often, however, the real value of the obstinate sulfur compounds lay in miniscule particles of included metallic gold.
Silver was also found at Bodie in other forms, though they were scarce. Silver chloride (called “horn silver”) was especially valued for the ease with which it responded to ordinary gold milling processes. Also rare was metallic silver (known as “native silver”), which occurred deep underground beyond the oxidizing effects of the atmosphere and water leaching from the surface. When discovered, solid silver attracted extraordinary attention and enhanced a mine’s allure.
NOTES
1. Sinking shafts and driving tunnels were feats also undertaken in coal and iron mining, but quartz mining’s western setting and glamorous metals made it more prestigious.
2. These figures are based on the district’s overall production for the year 1881, the height of Bodie’s mining prosperity, when gold was valued at $20.6718 per troy ounce, silver $1.2929 per troy ounce. Calculations using these prices indicate that gold made up 87% of the value of bullion produced from mines in the northern part of the district—Bodie Bluff and High Peak—whereas it made up only 47% of the value of the bullion from the south end—Silver and Queen Bee hills. Bullion from other districts contained base metals, such as lead, iron, or copper, but Bodie’s mining men recorded no such contamination. (California State Mining Bureau, Tables II and III, 398-401).
BIBLIOGRAPHY
California State Mining Bureau. Eighth Annual Report of the State Mineralogist, for the Year Ending October 1, 1888. Sacramento, CA: Superintendent of State Printing, 1888: 382-401.
Chesterman, Charles W.; Chapman, Rodger H.; and Gray, Cliffton H. Geology and Ore Deposits of the Bodie Mining District, Mono County, California—Bulletin 206. Sacramento, CA: Division of Mines and Geology, 1986.
De Quille, Dan [William Wright]. The Big Bonanza. 1876. Reprint, Las Vegas, NV: Nevada Publications, 1982.
Raymond, Rossiter W. “A Glossary of Mining and Metallurgical Terms.” In Transactions of the American Institute of Mining Engineers 9, Easton, PA: Institute of Mining Engineers, 1881: 99-192.
Smith, Grant H. “Bodie: The Last of the Old-Time Mining Camps.” California Historical Society Quarterly 4 (March 1925): 64-80.
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