Carl Henning

Refining Gold

As promised, a visit to the stamp mill in Bodie, CA. For an extra six bucks, tours of the stamp mill are offered. I enthusiastically participated; Kay found other activities. Ore came only from the mines owned by Standard Mining since they owned the mines and the mill.

Gold and silver are found embedded in quartz rock. The mill removes the gold and silver. It starts with rock crushing to reduce the size of the rocks to under four inches. Rocks that are larger than that pass completely over a grate system and are reduced in size by men wielding sledge hammers.

Then to the stamp mill. Here 20 thousand-pound stamps pulverize the rock. The stamp mill could be heard from three miles away. It must have been miserable in the town. The guide said that the mill ran six days a week and on Sunday mothers would have difficulty getting their little ones to sleep. They missed the “lullaby.”

Mercury was used to bind the gold and silver and separate it from the quartz. This collected on copper plates which were scraped to remove the putty-consistency results. The putty was heated to above the boiling point of mercury but below that of gold and silver. The mercury vaporized and was collected for reuse. Workers sometimes lost their hair, teeth, or lives due to mercury poisoning. Silver and gold were separated in a similar fashion. This process removed 60-80% of the minerals. So a lot was left in the mill tailings. Many years later the tailings were worked to remove the remaining minerals using cyanide.

Workers were paid $4 per day. A very high pay for the time. Dock workers in San Francisco were only making $2. This high wage attracted many would-be workers to town. So if a worker was injured or killed, he was quickly and easily replaced.

The mill owners greatest concern was clearly not worker safety; it was high-grading. High grading was theft of gold dust by the workers. They would hide it in the cuffs of their clothes, in their greasy hair, or wherever. The employer eventually forced all the workers to wear one-piece uniforms which they put on and took off in a communal shower under the foreman’s watchful eye.

The mill operated by steam power, using 20 cords of wood per day. Timber did not grow nearby; it had to be brought in by mule-drawn wagons. Until they built a narrow gauge railroad which ran the 13 miles from the lumber mill to the stamp mill. It did not connect to any main line. The railroad was salvaged for use in World War 1.

The mill owners were very forward thinking. They replaced the wood-fired steam engine with electricity… in 1893. Of course, that was the part that got this electrical engineer interested. So the next post will be devoted to electrifying the mill.

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.