Stamp mill
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A stamp mill (or stamp battery) is a type of mill 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.
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[edit] Usage
Stamp mills were used in early paper making for preparing the paper-stuff (pulp), before the invention of the Hollander beater. They were used in mining for breaking ore, and in oil-seed processing for prior to pressing the oil from the milled seeds. Early mills were water powered but mills can be steam, water, or electric powered.
[edit] Arrangement
A stamp mill consists of a set of heavy steel (or later, sometimes, metal-faced wood) stamps, loosely held vertically in a frame, in which the stamps can slide up and down. They are lifted by cams on a horizontal rotating shaft. Since the cam is on one side of the stamp, as it lifts it causes the stamp to rotate. This is important to ensure even wear to the shoe of the stamp. As the cam moves from under the stamp, the stamp falls onto the ore below, crushing the rock, and the lifting process is repeated at the next pass of the cam.
Each one frame and stamp set is sometimes called a "battery" or, confusingly, a "stamp" and mills are sometimes categorised by how many stamps they have, i.e. a "10 stamp mill" has 10 sets. They usually are arranged linearly, but when a mill is enlarged, a new line of them may be constructed rather than extending the line. Abandoned mill sites (as documented by industrial archaeologists) will usually have linear rows of foundation sets as their most prominent visible feature as the overall apparatus can exceed 20 feet in height, requiring large foundations. Stamps are usually arranged in sets of five.
Some ore processing applications used large quantities of water so some stamp mills are located near natural or artificial bodies of water. For example, the Redridge Steel Dam was built to supply stamp mills with process water.
[edit] History
Stamp mills were in use from the Renaissance period onwards. The first one in the U.S. was built in 1829 at the Capps mine located near Charlotte, North Carolina.[1] They were superseded in the 2nd half of the 19th century in many applications by more efficient methods of processing. 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) They were quite common in gold, silver and copper mining regions of the US in the latter half of the 19th and early 20th centuries, as the noble metals often occurred in metallic ores where physical crushing would give good separation results.
[edit] See also
- Hammer mill - A more modern device that also can crush material to fines.
- Ball mill - a horizontal cylinder containing metal balls to crush the material
- Stamp sand - the product of ore mills
[edit] References
- ^ see Mineral Resources of the Blue Ridge and Piedmont, page 143
[edit] External links
- Paymaster Stamp Mill near Lewiston, California
- 30 stamp mill near Cordova, Ontario
- Mining History Illustrations 5 cutaway drawings of mills produced by the Joshua Hendy Iron Works Company during the early 1900's.
- Copper Country ExplorerAn exploration of modern stamp mill ruins.
- Western Museum of Mining and Industry The historic "yellow jacket" stamp mill is located here. It is open year round, and operated several times per year for visitors.
