While Calaveras County is best known for its gold deposits, many other minerals have been mined in the county throughout its history.
In fact, at least 26 different minerals have been mined commercially in the county since the Gold Rush.
Although gold, copper and limestone mining have been by far the largest industries, zinc, chromite, lead, asbestos, talc, clay, sand, stone and gravel have also been produced successfully.
Gold mining in Calaveras County began with the Gold Rush, and carried on until most of the gold mines were shut down by government order during World War II. While some gold mining operations persisted into the later years of the 20th century, no large commercial gold mines continue to operate in the county today.
During the 1860s, Calaveras County became the second largest producer of copper in the country, thanks to rich deposits found around Copperopolis and Campo Seco. Spurred on by the military needs of the Civil War, the industry ebbed and flowed well into the 1900s, with production waxing during wartime and waning during peacetime. Zinc associated with copper deposits has also been produced in significant quantities. Today, small amounts of copper are still recovered from the waters of long-closed mines.
While the caves of Calaveras County first come to mind when discussing limestone deposits, the mineral was also mined successfully during the 20th century. From 1926 to 1983, the Calaveras Cement Company mined large amounts of limestone for use in the production of cement. The Kentucky House cement plant in San Andreas likely contributed more to area’s economy than any other single mining operation. The company’s old quarry at Cataract Gulch on Camp Nine Road is still considered a world-class limestone deposit. Its current owner, Lehigh Southwest Cement Company, plans to re-open the quarry when it again becomes viable economically.
Chromite production in the county peaked during World War I, when it was used locally to furnace linings in copper smelters. While small known reserves are still present, many in the Copperopolis area, the industry is unlikely to make a comeback unless new deposits are found.
Significant amounts of lead have also been produced in Calaveras County. Most lead deposits are associated with the copper deposits that run through Copperopolis and Campo Seco. Some lead has also been recovered as a by-product of gold mining.
Asbestos was produced in the county during the 1970s and 1980s, most being mined from the Voorhees deposit seven miles southeast of Copperopolis. The Calaveras Asbestos Company built a state-of-the-art mill at the site, and it briefly became the largest asbestos producer in the United States. The depletion of the ore body, as well as the discovery of the deleterious health effects posed by asbestos, brought the industry to an end. The old mining sites of the Voorhees deposit are now being used to store asbestos-containing waste and waste tires.
Talc has also been mined commercially in Calaveras County. During the 1970s, the talc mining division of Johnson and Johnson opened up a quarry between Carson Hill and Vallecito on Red Hill Road. After changing hands several times, the operation was brought to an end in 1997.
Clay, sand, stone and gravel are the most important mineral resources that have been extracted in the county in recent years, with most of the materials mined being used in the construction industry. The largest source of commercial clay is found in the Ione formation in the Valley Springs vicinity, while the most important sand and gravel deposits are found west of Valley Springs, in the northwestern corner of the county.
While there are roughly 11 commercial mines in Calaveras County with up-to-date permits, there are currently only four actively operating commercial mines in the county, according to the Planning Department. They mostly produce sand, stone, gravel and other materials for the construction industry.
At Hogan Quarry in Valley Springs, Ford Construction, Inc. produces stone to be used as riprap for jetties and levees, erosion protection and base rock for railroads, among other uses. Much of the material is shipped to Southern California by train, and production is currently much smaller than it was only a few years ago.
Ford also operates McCarty Pit in Douglas Flat, which currently produces limited amounts of sand and gravel. The historic pit is close to being entirely mined out.
At the old open-pit gold mine in Carson Hill, Carson Hill Rock is currently mining old waste piles, overburden stockpiles and heap-leach pads to process for road base and other aggregate. The company is also producing concrete and asphalt.
West of Highway 49 between San Andreas and Mokelumne Hill sits the Chili Gulch Quarry, which is operated by Charles Larson Construction. Over the years, the quarry has been mined for gold and rhyolite. Today, it produces limited amounts of sand and gravel for the construction industry.
While early mining in Calaveras County was done by adventurers hoping to strike it rich and head home, modern mining aims to produce the materials necessary to make homes here in the Golden State.
This article used information found in the 2018 Calaveras County Draft General Plan, Calaveras Gold by Ronald M. Limbaugh & Willard P. Fuller Jr., The Tools Are on the Bar by Charles and Rhoda Stone, and an interview with an official at the Planning Department.