California was referred to as “Gum Shan,” or “Gold Mountain,” by the tens of thousands of Chinese who risked everything to travel to the Mother Lode.
We know that a mountain of gold is a great exaggeration, but looking back at the statistics it was, in fact, at least a small hill of the precious metal.
More than 93 tons of gold were extracted from the Sierra Nevada foothills in 1853. By 1858, the Mother Lode had yielded 973 tons of the precious metal. Geologists estimate that more than 3,634 tons had been extracted by 2008, the 160th anniversary of the discovery of gold on the American River.
In a very short span of time, the quest for gold moved from individuals panning for gold to the construction of deep mines through hard rock and massive hydraulic mines that eradicated cubic acres of the Sierras, leaving only moonscape like canyons behind.
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In last week’s Times Past we recounted how the rivers flowing from the Sierras were clogged with debris from hydraulic mining. This led to unprecedented flooding of the Sacramento and San Joaquin valleys beginning in 1862. My mentor and friend Robert L. Kelley has told the story of how the valley farmers united to stop much of the hydraulic mining by 1884 in “Gold Versus Grain: The Hydraulic Mining Controversy in California's Sacramento Valley” (1959).
But there was another environmental hazard from unfettered mining with a link to the Central Coast: Mercury pollution of the Sierra streams.
Coarse gold- and silver-bearing ore was taken from the mine or hydraulic operation to a steam- or water-powered rock crusher and stamp mill. The ore was crushed to the consistency of gravel and then would slide down onto metal plates situated under the stamp battery where water would push it under a set of five or more stamps. The ore was pulverized into a fine sand.
The slurry mixture was pushed over a recovery table, a copper-sheeted table coated with mercury; the gold in the sand would stick to the mercury. The amalgamated gold and mercury mixture would be removed by straining it through a chamois and sent to a retort where the mercury would be boiled off and mostly recovered, leaving gold bullion.
The process required lots of mercury. California’s first source of cinnabar or mercury ore was the New Almaden Mine on the southwestern edge of the Santa Clara Valley. Discovered in the 1820s, it was named after similar mines in Almadén, Spain. The Almaden had a monopoly on mercury production until the New Idria mines were opened in the Gabilan Range east of Soledad in 1854.
The monopoly held by these two operations on mercury production reached a climax during the American Civil War when mercury was also needed for percussion caps on rifles and other explosive devices.
The rising prices led mining entrepreneur and future U. S. Senator George Hearst to acquire Rancho Piedra Blanca on our North Coast in 1865. He knew from the Salinan Indians and local residents that the brown sandstone (“Franciscan Layer”) in the Santa Lucia Mountain Range was loaded with cinnabar. Soon the coastal foothills were busy mining for what gold and silver mining districts needed most.
Mercury extraction was even used by small-scale miners in small “amalgamating boxes” containing mercury. The U.S. Geological Survey estimates that 7,600 tons or 15,200,000 pounds of mercury were thus deposited into the lakes, creek and rivers flowing down from the Sierra Nevada.
It was no wonder that some of California’s earliest state institutions were homes for the insane. Another environmental crisis had to be dealt with.
Readers are invited to join the San Luis Obispo Mission Museum Docents on a trip on the “Times Past Highway through the Mother Lode.” We will be visiting the important and colorful sites of California’s Gold Rush era from Columbia to Grass Valley and Nevada City, October 15-17. Contact Silver Bay Tours at (805) 772-3409.