By any measure, the most important mineral in the history of the Cambria area is mercury, also called quicksilver because of its silvery color and the fact that it occurs in a liquid state at room temperature.

Throughout history, mercury has had a wide variety of uses including the preservation of wood, developing daguerreotypes, silvering mirrors, making of felt hats, manufacturing of batteries, and the production of chlorine and caustic soda. In spite of its toxicity, mercury has been used as an antiseptic, especially in mercurochrome and merthiolate, a laxative, an antidepressant, and as a treatment for syphilis.  Because mercury does not adhere to glass, it has found wide spread use in thermometers, barometers, manometers, sphygmomanometers, float valves and thermostats.

Even today, it is widely used in the manufacture of mascara and in dentistry as well as in mercury vapor lamps and fluorescent lamps including the modern day compact fluorescent bulb. Some of its more exotic applications have been as a coolant in nuclear reactors and in ion propulsion electric rocket engines.

Mercury has long been used extensively in the mining of gold where it forms an amalgam with gold helping to separate the metal from impurities. Yet another major application of mercury was in ammunition in the form of  fulminate of mercury. Mercury is still in use for both military and civilian applications as a primer for all sorts of high explosives.

Cinnibar crystal

Mercury is an extremely rare element. Generally, its total mass is only .08 parts per million of the earth’s crust. However, because it does not chemically combine with most of the surrounding elements, it is sometimes found in highly concentrated amounts. In the United States, more than 85 percent of all mercury produced has come from California and 71 percent came from eight mines in this state. In San Luis Obispo County, mercury deposits have been found along both sides of the Santa Lucia Mountains from the extreme northwest corner of the county southeasterly to the Santa Barbara County line.

Quicksilver deposits in the Cambria area consist of irregular and discontinuous veins of cinnabar and rock masses containing disseminated cinnabar. Cinnabar is a crystal composed of mercury sulfide which occurs in various shades of dark red.

To extract the mercury from cinnabar, the ore is first crushed to a size of about one to two inches.  Extracting the mercury from the crushed ore follows a simple principle. The ore is heated to drive out the mercury and the resulting mercury vapor is condensed to a liquid. This process is inexpensive and can be carried out at the mine site avoiding shipment of the ore. In practice, a wide variety of processes were employed to implement this principle.

Rossi Retort with two condensing pipes

The simplest process is a retort in which the ore is placed in a closed container and heated by an external source such as a wood or oil fire. The resulting mercury vapors are passed through one or more iron pipes to condense it. A retort is inexpensive to build but it has a small capacity and operates intermittently. When the charge is consumed, it must be shut down and re-charged.

The furnace is a different process for extracting mercury from the ore. In a furnace the fuel is mixed with the ore and then burned in a continuous process. As the ore and fuel are consumed, more is added and the residue, called calcine, is continuously removed. Several types of furnaces have been used in the Cambria area including the Scott, Herreshoff and several types of rotary furnaces.

Mercury derived by any of the above methods was collected in iron flasks containing 76 pounds of mercury. Because mercury has a density 13.6 times greater than water, a flask of 76 pounds of mercury contains only about 2.5 liters of mercury or a little over one half gallon.

Over the years, the price of mercury has fluctuated greatly in response to changes in demand. Mercury mining in the Cambria area has been sporadic and in the United States it ceased entirely in 1990.

The earliest indication of mercury mining in the Cambria area occurred in 1862 when the Little Bonanza deposit was discovered. During the next fifteen years, most of the known deposits were located and worked.

The Little Bonanza was actually a small group of mines which included the Little Bonanza, Alice, Modoc, Josephine and other claims located near the top of the Santa Lucia Mountains roughly half way between Cambria and Paso Robles. These mines produced over 1,000 flasks of mercury even though they were only worked sporadically between 1862 and 1940. In 1915 and 1916, the Little Bonanza Mine was operated by Elmer Rigdon and Eugenio Bianchini.

The Oceanic Mercury Mine

By far the largest mercury mine in the Cambria area was the Oceanic Mine which covered 400 acres and was located five miles up Santa Rosa Creek from Cambria. It produced at least 38,000 flasks of mercury, nearly as much as all other mines in San Luis Obispo County combined.

The Oceanic mine was located in 1865 and the patent document was signed by Abraham Lincoln. Large scale operations began in 1875 but falling mercury prices caused production to cease in 1882.  Production resumed in 1902 and the mine was worked intermittently until 1926 when it was acquired by H. W. Gould. Gould leased the mine to the International Mercury Company of Los Angeles for two years and, in 1928, they took over operation of the mine. After two more years the mine was sold to the Consolidated Metals Corporation in 1930 and they did considerable development work at the facility but it was again closed in 1932 due to the plummeting price of mercury. The assets of the company were taken over in 1933 by the Anglo-American Mining Corporation, Ltd. who reopened the mine from 1934 until 1946. In 1954 work was resumed but the mine was finally shut down in 1958.

The second largest mercury mine in the Cambria area was the Klau Mine located about seventeen miles northwest of Paso Robles. Opened in 1868, this mine yielded nearly 18,000 flasks of mercury by 1940 even though it operated during only 35 of the 72 year period.  In 1902 alone, the Klau mine produced 3,300 flasks.

When World War I broke out, the demand for mercury increased and Eugenio Bianchini decided to take up mining once more. In partnership with Antone  Luchessa and William Bagby, he purchased the Klau mine and he was put in charge of operating it. By 1917 the mine was averaging a flask a day. The mine was operated again between 1943 and 1947 and intermittently after that but all of the equipment had been removed by 1965. Total production from this mine amounts to about 24,000 flasks.

The Buena Vista or Mahoney mine, about 16 miles northwest of Paso Robles, was the third biggest producer in the Cambria area. It was first located in 1874 but mining operations did not start until 1900. It was operated intermittently until 1948 with most of its output occurring after 1942. The mine was reactivated in 1953 and was operated sporadically well into the 1960s. The Buena Vista mine produced more than 15,000 flasks of mercury.

Although it was much smaller than the Oceanic, Klau or Buena Vista mines, the Cambria Mine was the fourth biggest producer in the Cambria area yielding more than 4,000 flasks of mercury, nearly all of it between 1903 and 1917. The Cambria Mine was located on the north side of San Simeon Creek about three miles from the ocean. The mine was first worked by Elmer Rigdon in 1903 and he sold it in 1906 to H. R. Gage and C. W. Carson.

The La Libertad mine was located near the intersection of Santa Rosa Creek Road and Cypress Mountain Road. The site was located in 1901 but was only worked for two years. Further operations occurred during 1915 and 1916, 1935, 1947 and 1948, and again in 1952. Total production was about 1,100 flasks.

The Polar Star mine was actually a group of nine mines located about three miles up San Carpoforo Creek about 13-1/2 miles north of San Simeon near the Monterey County line. The deposit was discovered in 1870 and worked intermittently until 1900 and again in 1915 but little mercury was produced. However, between 1936 and 1946 the price of mercury jumped due to increased demand caused by the Spanish Civil War and World War II and several hundred flasks were produced at Polar Star. The mine was reactivated between 1955 and 1958.

Other quicksilver mines of lesser importance in the Cambria area included the Hamilton mine, the Keystone mine and the Pine Mountain group of mines which included the Pine Mountain, Buckeye and Ocean View mines  located about 12 miles north of Cambria.

The Quien Sabe mine, including the Doty mine, consisted of five claims about 16 miles from Cambria. They were discovered in 1905 and worked sporadically until 1917 producing a small amount of mercury. Some further work was done at this site during 1955 and 1956.

9 Responses to “Quicksilver”

  1. Pete Shyvers says:

    Perhaps you could find a county coroner’s report on your great-grandfather’s death. That might give some clues, or even answer the question.

  2. Dianne Dotson says:

    How do you go about obtaining names of individuals who may have worked at the Klau Mine. My grandmother (last name Spreafico) and her family lived at the mine and i think her father died there. My father told me that some of the family was buried there. Thank you.

  3. B&J says:

    She is my Grandmother. I remember when you read the proclamation. She had such a good time at that party.
    She lived to 102 and in good health until about 2 week until she passed.


  4. B&J says:


    As the official Town Criers of San Luis Obispo County we read a proclamation a few years back for the one hundredth birthday of Linda Hampton, a local resident. Her maiden name was Linda Luchessa. Was she a relative of yours?


  5. DGL says:

    My Great Uncle Aldo Luchessa died in a mining accident there.

  6. B&J says:

    When you said, “The old retorts did not perfectly remove the mercury from the ore…” that could be an understatement. The efficiency of mercury extraction varied greatly and some mine tailings, called calcine, still contained up to half of their original mercury. This material was either placed in the dump or, in some cases, into nearby streams which washed it away. The result is potential contamination of the water and its inhabitants for several miles downstream.


  7. David Houtz says:

    My dad, Roland Houtz and a grading contractor, Mark Gates worked the old retorts at the Oceanic mine during WWII when no regular construction jobs were possible. The old retorts did not perfectly remove the mercury from the ore, so dad and Mark “mined” the floor of the retorts and recovered a lot of mercury.
    I used to put some of it in bowls and play with it. That was before we learned of the dangers of Mercury.

    I understand that Abe Lincoln signed the original grant for the Oceanic mine. It might be worth checking out.

    After working the Oceanic, dad and Mark worked at the old retorts of the Polar Star, on the Hearst Ranch.

  8. B&J says:


    We’re not clear which mine you’re talking about but it doesn’t much matter because we have no lists of employees at any of the mercury mines in the area. We did a quick check of the census records and we couldn’t find any Melero’s in this area. However, the most recent census record available on line is the 1930 census. We think the 1940 census can be viewed at the National Archives regional office nearest you or your local genealogical society.

    Sorry we couldn’t be of more help.

  9. Larry Melero says:

    I just found records that my father, Leopoldo (Avitia) Melero worked at the mine in 1930, Do you happen to have records of employees that date that far back? I would like to pursue this information and anything you could provide would be appreciated. I basicly have no information of my father past my birth in 1941. Thank You

    Larry Melero

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