El Dorado Mine
To find gold veins beneath the surface tunnels were dug and ore was brought out and crushed at the stamp mill. This was an example of hard rock mining. In 1885, William Paul found gold near the present El Dorado Mine. The shaft he dug eventually reached 500 feet in length, comparable to 1 and 2/3 of a football field.
At the stamp mill, a large iron pestle, weighing over a ton was lifted by pulleys and then smashed the rock until it was powder. This stamp would pound about 90 times per minute, rattling the whole building and deafening the miners. Water was mixed with the powdered ore washing along the metal apron at the base of the mill. This metal sheet was treated with mercury, which attracted the gold, pulling it out from the excess rock. After, the mercury and gold were scraped up and heated together in order to drive off the mercury and leave the gold. The poisonous mercury vapors were trapped in a tube, condensed, and used over again. The excess rock dug out of the tunnel was dumped on the ground as tailings. Miners had to know how to use dynamite, needed expertise in geology, engineering, and hard-rock mining and milling. It was expensive to set up a mining company, and miners were paid $2 to $4 per day to work in the mines. Although several thousands of dollars’ worth of gold was removed, mining was never a large operation. The mine was actively worked until 1967, when it was acquired by the National Park Service from the Bickford family.
