Giant Gold Machines - Hard Rock Mining
Much of the Sierra Nevada's gold is encased in quartz veins deep within the mountains. To reach these veins of gold-bearing quartz, hard rock miners tunneled and sank shafts deep into mountainsides. Imagine what it was like to work thousands of feet below the surface. Thousands of miles of tunnels were dug beneath the mountains and shored up with Sierran timber. Miners blasted and dug their way through the mountains, and descended in mine cars, cage-like elevators, to fill buckets and ore cars with quartz rock. This was dangerous work: cave-ins, explosions, toxic fumes, and flooding injured and killed many.
rock miners had to mill, or crush the quartz ore. They worked stamp mills to pulverize the
ore to a powder. Early stamp mills had two to five stamps. Later, banks of forty or more
were used. Gold was then separated from this fine powder by the use of mercury, or
quicksilver as it was called. Despite the efforts of miners to recover their valuable
mercury, tons of mercury were being washed down from the mountains. Mercury is very toxic,
especially when heated to a vapor, or incorporated into the food chain. Fish and wildlife
deaths from the release of mercury and other toxic mining
discharges were common. Large quantities of mercury still remain in the sediment layers of
the rivers and in San Francisco Bay, a toxic legacy of our mining heritage.
Top: Stamp Mill, Photo by Christopher Richard
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