page_title: Stamp mill
section_title: 19th century
hierarchical_section_title: Stamp mill / History / 19th century
caption_attribution_description: English: Image taken and uploaded by User:Leonard G.. Five stamp mill for crushing ore, located at the Jerome, Arizona Mining Museum. thumb|right|200px|Detail showing offset cams to rotate lifters for even wear on this particular type
context_page_description: A stamp mill is a type of mill machine that crushes material by pounding rather than grinding, either for further processing or for extraction of metallic ores. Breaking material down is a type of unit operation.
context_section_description: The first stamp mill in the U.S. was built in 1829 at the Capps mine near Charlotte, North Carolina. They were common in gold, silver, and copper mining regions of the US in the latter 19th and early 20th centuries, in operations where the ore was crushed as a prelude to extracting the metals.  They were superseded in the second half of the 19th century in many applications by more efficient methods. However their simplicity meant that they were used in remote areas for ore processing well into the 20th century. (19th century advertisements for some mills highlighted that they could be broken down, packed in by mule in pieces, and assembled on site with only simple tools.) Stamp mills are still in use in Colombia by artisanal miners, powered by electric motors. 
  Cornish stamps are stamp mills that were developed in Cornwall for use in tin mining in around 1850. Cornish stamps were used to crush small lumps of ore into sand-like material.  The stamp was constructed from heavy timber with an iron "head" at the bottom. It was lifted by cams on a rotating axle, and fell on the ore and water mixture, fed into a box beneath.  The head normally weighed between 4 and 8 cwt  (about 200 to 400 kg) each, and were usually arranged in sets of four, in timber frames.  Small stamps were commonly powered by water wheels and larger ones by steam engines.
  Californian stamps were based on Cornish stamps and were used in the Californian gold mines. In these stamps the cam is arranged to lift the stamp from the side, so that it causes the stamp to rotate. This evens the wear on the shoe at the foot of the stamp. They were more rapid in action and a single head could crush 1.5 tons of ore as opposed to the Cornish stamps which could only crush 1 ton.
caption: A five unit Californian stamp mill once used in Arizona for crushing copper ore.
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