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Hard Rock Mining, Pt. 2
Submitted By: XNGH Jason Thorn Date: March 21, 2010, 08:06:51 AM Views: 1841

Originally published in the Hewgag Monitor by Tom Barry in October, 1993

We continue now with our short history of E Clampus Vitus, or in this case, the third part of a short primer of Gold and the second part about hard rock mining.

We tend to think only of California when we think of the Gold Rush, but in actuality, California only produced about $1.25 billion in gold by 1900. Production at the Homestake Mine in the Black Hills, alone, has exceeded $1 billion over its lifetime. $340 million was taken from 475 mines in Colorado in a 36 square mile area at Cripple Creek.

Mining in various forms has been practiced by mankind for thousands of years, but many of the more sophisticated mining methods were not developed until the latter part of the 19th Century. In mining, as in most other fields of human endeavor, man’s ingenuity was put to the tasks of improving output, easing labor and increasing safety and profits.

As mentioned previously, once the easily obtained placer gold deposits were taken from the stream beds, the miners looked upstream and uphill for the source of the gold nuggets and dust.
If that source was an ancient gravel bed, the miners could dig the gravel by hand and pan it near a source of water. If the gold source was not rich enough to justify the hand digging and panning, hydraulic mining processes could be used. But if the source was a hard rock deposit such as quartz, the rock would have to be removed and then transported to crushers and stamp mills where it would be reduced to fine sand, and then treated chemically to extract the gold.

As the miners proceeded deeper into the earth, certain problems came to light. If the pay dirt was in the form of clay, or loosely consolidated gravel, cave-ins were likely. Shoring, in the form of lumber supports at varying intervals along a shaft, was sufficient for most hard rock mines. But in mines such as those in the Comstock Lode in Nevada, even this proved to be unsatisfactory, as the “vein” being followed sometime became 40 to 50 feet wide, making it impossible to shore up in this fashion.

A new form of shoring in unstable ores, called square-set blocking, was developed by a German mining engineer named Philipp Deidesheimer in these mines in 1860. Utilizing a standard set of timbers, 14 x 14 inches by 6 feet long, mortised and tenoned at the ends, boxlike cubicles could be constructed which, when planked, would allow men to stand and work the face of the ore for a distance of 6 feet, then another “set” would be installed and planked, allowing another 6 feet to be worked. This process could be extended vertically and horizontally in any direction, allowing the miners to follow the drift of the vein of pay dirt with relative safety. The need for lumber for this and other mining operations around Virginia City created a logging and related hauling industry to supply 80 million board feet of lumber for timbers a year, plus 250,000 cords of wood to be burned in the numerous large steam engines for winches, crushing machinery and stamp mills. This was necessary because there was no source of falling water to be able to use water-powered devices, which were relatively underpowered in any case. It wouldn’t be until after 1878, when Lester Pelton, of Camptonville, would invent the most efficient and useful Pelton wheel, the design of which is still used today. Then, water powered wheels would have enough efficiency and power to operate air compressors and electrical generators in places where water was available.

Other innovations, involving the outlay of large sums of money, were developed. To remove water from the mines, huge pumps were built. One giant stationary steam engine used for pumping water had two immense cylinders, one being 100 inches in diameter, with a stroke of 8 feet. This 43 ton engine had a flywheel 40 feet in diameter, made of cast iron. To this colossal engine was attached a half-mile-long pump rod (made of wooden beams bolted together) extending down a mine shaft. It made a leisurely 10 strokes a minute, but could lift 2 million gallons of water from the mine each 24 hours.

A proposal in 1864 to dig a tunnel to drain the mines was made in the Gold Hill News. One man, Adolph Sutro, a former ore reduction plant owner, began the task of financing and building a tunnel from the lode to the river, about 4 miles long. His investment would be recouped from the mine owners, who would pay $2 per ton on all ore they produced for the removal of water from their workings. However, its construction was long delayed due to financing difficulties and upon its completion, was too late to have a great affect on the cost of mining the Comstock Lode. By that time, in 1878, the greatest part of the Lode had been removed. Sutro, however, was able to sell his stock before its value plunged and he retired, a millionaire, to San Francisco, where he became a patron of the Arts and a civic leader of the highest stature.

Another problem in the Virginia City mines was the heat from underground magma chambers near the digging. Steam and hot water issued from the mines as the ore bodies were being followed deeper.

Ice (up to 95 pounds per man, per day), was brought into the mines to allow miners to work the deeper reaches of the tunnels, where the temperatures rose 5 degrees for each 100 feet of depth. At the 3000 foot level, 165 degree water spurted from drill holes, and wooden pick handles were too hot to handle with bare hands. Men were able to work only 15 minutes of each hour, or risk death due to heat prostration. Many were scalded to the point of death by falling into pools of this water underground.

Lifting machinery played a very important part in the operation of deep mines. To raise the immense tonnages of rock to the surface required the constant operation of, what would seem to us, quite primitive, equipment. Miners were lowered and raised by open elevator cars riding in shafts only a few inches larger than the cars. An errant hand gesture or the accidental misplacement of a foot often resulted in the agonizing dismemberment of the offending limb.

Operators of the lifts, seated at the lifting controls above ground, received signals from each level by a bell, which was rung in code, by a rope hanging down the shaft. The ability of the engineers, as they were called, to stop a car at exactly the right spot was a highly praised and appreciated skill. The engineers could not divert their attention from their equipment for even a moment, or someone could die. They were the most trusted individuals in the mines.

Ore was brought up in small carts, holding a ton or so each. In some instances, the ore cars rode up a steep incline, and the tracks could be a bit bumpy, causing rocks to fall out. The resultant deadly missiles could fall hundreds or thousands of feet, often with fatal results. In like manner, the drill rods had to be hauled to the blacksmith for resharpening very often, and they could fall down a shaft with unbelievable force. Even a dog, misjudging a jump across an opening, killed 2 miners when it fell 300 feet down a mineshaft.

The constant danger of cave ins, bad air, silicosis-causing rock dust (miner’s consumption was the name given to these lung diseases), having something fall on you, including your fellow miner, and the other generally unsafe conditions in the mines meant that the man who spent 10 years in mining stood a 1 in 3 chance of being seriously injured and a 1 in 8 chance of being killed. In all, probably 7500 miners were killed and another 20,000 were maimed during the pioneer days of the western gold and silver mines.

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