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El Casa Grande |
While moored at Brisbane Marina, we rented a car and drove to the town of
New Almaden to visit El Casa Grande.
This
grand house, once a residence for a succession of mine managers and their families,
is now the home of the New Almaden Quicksilver Mining Museum.
Dedicated to the history, geology, and mining
communities of New Almaden, the museum provides a glimpse of life in Santa
Clara County 150 years ago.
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Beautiful Rooms in the Casa |
Rooms of the
home display period furniture and artifacts of daily living, while another
portion of the home depicts the region’s mining history through photographs
taken by a doctor who witnessed one of the world’s largest mercury-mining
operations of its time.
Mining
operations in New Almaden first began in 1845 under the claim of Mexican
Cavalry officer Captain Andres Castillero.
Castillero discovered that the red rock was cinnabar, an ore containing
mercury.
Considered a valuable commodity,
mercury was needed to process silver in Mexican silver mines and later to
process gold discovered in California.
Mercury,
also called “quicksilver” is still used in levels, thermometers, lamps,
barometers, batteries, electronics, medicine, and agriculture.
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Cinnabar |
The red rock harvested from the hills of New
Almaden spawned a thriving economy and several settlements in the area.
American companies eventually acquired
ownership of the mines, where operations continued under the management of
Captain Henry Halleck.
Halleck had the
Casa Grande designed and built in 1854, which served as the official residence
and office of a succession of mine superintendents for several decades and was
also used as a weekend retreat for wealthy mine investors.
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Efficient Processing with Furnaces |
The earliest processing of cinnabar ore at
New Almaden was done by heating the ore in huge metal “whale pots” to extract
the mercury, a crude but effective method due to the richness of the ore
(sometimes more than 60 percent mercury).
After the richest ore was depleted, the ore had to be roasted to recover
the same amount of mercury from far greater quantities of low-grade ore.
Small batches of mercury could be extracted
by using a retort, a device similar to a moonshiner’s still.
Large furnaces and condensers improved and
evolved so more mercury could be recovered from each ton of ore; however, the
furnaces had to be cooled periodically and cleaned out before starting another
batch – a time-consuming, labor intensive process.
An experimental furnace, constructed at New
Almaden in 1874, revolutionized ore processing.
This new reduction process allowed ore to slowly trickle into the top of
the furnace.
Gravity then brought the
ore slowly down a vertical shaft and out the bottom while its mercury content
was vaporized, condensed, and collected.
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Filling Iron Flasks with Mercury |
During the late 1870’s, New Almaden produced more mercury than any other
mine in the world.
The New Almaden Mine
produced 83,974,076 pounds of mercury until the operations ceased in 1976.
Long after innovative methods of processing
ore became available, miners at New Almaden continued to use primitive methods
to obtain the ore – blasting with black powder and drilling holes by hand with
one-inch steel bits.
More than 50 miles
of tunnels honeycomb the hills of New Almaden, nearly all were built by
hand.
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Cinnabar Ore Mine Shaft |
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Stacks of Wood Beams used for the Tunnels |
The mine property and the Casa
Grande make up the Almaden Quicksilver County Park with miles of trails,
remnants from the past, and informative plaques describing the communities of
Mexican, English, and Chinese miners and their families.
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Cinnabar Paste Used for Design |
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Red Dots show Cinnabar located around the World |