75. Introduction to Blasting and Explosives in Mines / National Mining Museum, Leadville, Colorado

And finally, this display appears in the National Mining Museum in Leadville.

"Introduction to Blasting and Explosives in Mines"

"Between the 1830's and the 1850's, explosives became a permanent fixture in mines;  it reduced the cost of mining and helped increase productivity.

"Black powder was first adopted in America mid-17th century with the opening of the first black powder mill in Massachusetts.  It was used by the settlers to help provide food, ignite fires and for protection.   During the same period, black powder was used extensively in German mines, and by the late 17th century, its use in the mining industry had spread as far as Cornwall, England.   Later, during the mass immigrations of the 19th century, the Cornish miners (also known as 'Cousin Jacks') brought this technology and their blasting techniques to America.  They also brought the miner's candlestick, lunch bucket, and the code of signals that enable the hoist man to communicate with the miners underground.   The sudden increase in popularity and blasting usage in the mines spread quickly and powder mills were established to meet demand.

"Black powder was the only explosive used in mines until the introduction of Nitro-glycerine, and then dynamite..."  

74. Black Powder / National Mining Museum, Leadville, Colorado

Another exhibit from the National Mining Museum at Leadville, Colorado, has a simple description and explanation of black powder.   In the early gold mining efforts in Colorado, black powder was used to blast into rock crevices, dislodging the material, allowing it to be removed and processed (from which gold, if it were present, would be extracted).   The words below are taken exactly as they are displayed in the museum.  

"Black Powder"

"The term black powder was first used in the late 19th century to help distinguish between the different types of powders, e.g., gunpowder, semi smokeless powder, etc.   It was used in mines by igniting it in drill holes and cracks in rocks.

Black powder is a mixture of three components: 

1.  Potassium Nitrate:  other names include Salt Peter or Nitre
2.  Sulphur:  a bright yellow crystalline solid
3.  Charcoal:  a black substance made from burnt wood that has been deprived of oxygen and leaves an impure carbon residue

"Potassium Nitrate and Charcoal create a minor explosion, but when mixed with sulphur, the explosion is much stronger.

"Mixing all three components together form a group of gases:  carbon dioxide, nitrogen (both colorless and odorless) and potassium sulphide (a compound that reacts rapidly with water).

How it works

"When the three components are mixed together and ignited, the gases form a heat.   This heat forces the gases to expand causing an explosive force."

73. Stamp Mill / National Mining Museum, Leadville, Colorado

After walking through the excellent National Mining Museum in Leadville, Colorado, two weeks ago, and discovering an exhibit -- a diorama entitled, "Stamp Mills and Amalgamation" -- I wanted to incorporate the vignette of American gold mining into this blog in order to help us better understand the history of Swiss black powder milling as it pertains to the Treuthardt family (which will be described in forthcoming posts).  The display at the National Mining Museum was written exactly as follows:

"Stamp Mills and Amalgamation"

"As the mines went deeper and brought up larger quantities of ore, the arrastras* could no longer keep up.   Businessmen realized that stamp mills would be profitable ventures.   Stamp mills became the primary means of breaking and processing ore, and owing to the introduction of the amalgamation process, were a step forward in gold mining technology.

"At the top level of a stamp mill, larger metal grinders pound the ore into fist-sized chunks.   A step below, the chunks are smashed in water by half-ton stamps.   The resulting slurry passes through screens and drops into amalgamating pans.   How amalgamation works on a physical and chemical level is not clearly understood to this day, but it is known that if mercury is brought into contact with gold, the gold is 'drawn into' the mercury.   This results in an alloy of gold and mercury called amalgam.   After the mercury has gathered in the gold, the mercury can be removed by dissolving it in nitric acid or heating it to a vapor." 

*ARRASTRAS
Here (since we were wondering) is a description of arrastra, below, written by Kenneth Jessen.   For the rest of the interesting article, see this webpage.  

http://www.reporterherald.com/ci_21960868/arrastra-remains-near-buena-vista

"An arrastra, in its simplest terms is a grinder and dates back to the fifth century B.C.   The grinding surface is typically flat bedrock situated near a stream. A vertical pocket is drilled into the rock and a pole is placed in the pocket. Attached to the pole near its base is an arm and attached to the arm, usually by chains, are heavy drag stones. Farther up the pole is a long horizontal beam that is used to turn the center pole.  As the pole is rotated, the heavy drag stone do the grinding against the bedrock surface. Small arrastras could be human powered and draft animals were used to turn larger examples. The most common use in Colorado was to grind ore containing gold flakes. The ore was placed on the grinding surface and after hours the ore is pulverized into a fine powder. A small amount of mercury is added during the process to amalgamate the gold. The gold-mercury amalgam settles to the bedrock while the worthless rock is washed away using water from the nearby stream. The amalgam is then collected and strained through a cloth to remove most of the mercury leaving behind a gold button. The remaining mercury is driven off in a retort, condensed and reused. The gold requires further refining to remove the remaining impurities. Arrastras were used in the absence of large, efficient gold mills or in remote locations. They are very limited in the amount of material that could be processed.

"Arrastras in Colorado are rare. Many have been cut out of the bedrock and moved to museums. One example, still in its original location and relatively easy to reach, is north of Buena Vista on Fourmile Creek. It requires only a short walk from a four-wheel drive road."

"Kenneth Jessen has been a Loveland, Colorado, resident since 1965. He is an author of 18 books and more than 1,300 articles. He was an engineer for Hewlett-Packard for 33 years and now works as a full-time author, lecturer and guide."

(See also my related post #72.)