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Mining in the mid 1800's in the West was changing according to the nature of the ores that were encountered. In the early days of hard-rock mining, a miner needed extremely rich ore in order to justify the labor and expense in recovery, processing, and transportation. Ore in which the minerals were "free milling" meaning that the precious metals were not in combination with other substances were the only ones which could be mined economically. When you read of a rich mine located during these early days, try to imagine the prospector who decides to crack open a piece of quartz only to find it studded with grains of gold. Working to open up a seam of ore required backbreaking work using nothing more than a sledge hammer, hand drill, and a shovel to move material. As the mine deepened, the lone miner could no longer afford nor might he even know how to continue digging deep into the earth. He would inevitably sell his prospect and move on trying to discover another bonanza. Enter the mining speculator.
Deep mining required the use of large teams of miners and money to buy wood to shore up the tunnels driven deep into the earth. Although most of the actual digging was done using the same methods that the lone miner would use, teams of men would work together, one holding the hand drill and the other pounding away with the sledge hammer. In a single shift lasting anywhere from 8 to 12 hours, the miners would usually be able to drill several holes in the face of the tunnel. They would then set charges of black powder in the holes, lighting the fuses, and blowing a foot or two of rock off of the end of the tunnel. It was up to the next shift to come in and "muck" up the rock ore and send it out by wheel barrel in the smaller mines or by an ore cart in the larger ones. The ore cart might be hand-pushed along small scale railroad tracks to the ore bin located somewhere outside the mine entrance. Sometimes mules were used to move the ore carts throughout the mines. The broken rock would then be sent to a crushing mill to be pulverized to a very fine powder. If the mine was rich enough, the owners would install a stamp mill on site. Otherwise, the ore would be sent to an off site mill operation. If the ore was sent out for processing, many times only the richest, hand-sorted ore would be sent.
| A two stamp, stamp mill on display at Laws Railroad Museum located at Laws, California just outside of Bishop, CA. |  |
At the stamp mill the ore was crushed to a very fine powder, mixed with water and some "secret" reducing agents and then mixed with mercury. Gold would adhere to the mercury and the rest of the rock powder could be washed away. That fine powder can be seen below most milling sites throughout the west as huge flows of light grey to brown plateaus of dirt. The mercury was usually heated to a vapor and collected in a condenser, leaving mercury coated gold behind. Because of the need for water to help move and process the ore, much of the mercury would find its way into streams and rivers from which we are still trying to clean up. Mercury was even used on smaller scales by individual miners to collect fine gold. The mercury-gold mixture could be literally rung out of a cloth leaving the gold behind and most of the mercury could be saved. In the late 1800's and early 1900's the crushing of ore was sometimes done by what was known as a ball mill. The ball mill was a large cast iron pan which rotated and inside were cast iron balls similar to cannon balls. These balls would roll around crushing the ore in their paths.
One of the biggest improvements in processing ore which is still being used today is the collection of gold using a very weak solution of cyanide. This process has allowed the recovery of minute of amounts of gold that the old time miners could not have begun to retrieve. Another improvement with a somewhat dubious distinction, was the air-powered drill. This drill allowed a single miner to rapidly drill holes in the rock face for blasting. The early models were used dry while later units had water added for both cooling the drill bit and reducing the amount of silica dust that would be produced by the high speed drills. Without proper ventilation, the dust would clog the lungs of miners using dry methods of drilling producing a lung disease known as silicosis, which killed hundreds if not thousands of miners. I once met an old time miner in New Mexico that had been struck with this disease. He ran a small rock shop for tourists but was continually tied to an oxygen bottle to help his damaged lungs.
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An air powered rock drill on display in Virginia City, Nevada. |
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