Stamp mill

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Section of Quincy Mine unit operations diagram showing Allis Steam Stamp Mill

A Stamp mill 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.

1 Usage
2 Arrangement
3 History
4 See also
5 References
6 External links

[edit] Usage

A five unit Californian type stamp mill once used in Arizona for crushing copper ore. The large wheel was turned by a belt connecting to the power source. The cams lift and release the weights which fall by gravity.

Stamp mills were use 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.

Interior of the Deadwood Terra Gold Stamp Mill. Crushed ore is washed over mercury coated copper sheets, whence fine gold particles form an almagam with the mercury. The almagam was scraped off and the gold then separated from the amalgam by heating and evaporating the mercury which was then recovered by a condenser for reapplication to the plates

[edit] Arrangement

Stamp mills comprised a set of heavy wooden (or later, steel) beams with a metal facing on the bottom, loosely held vertically in a frame, in which the beams could slide up and down. They were lifted by cams on a horizontal rotating shaft. As the cam left the beam it fell onto the material being processed, then picked up again at the next pass of the cam. Each frame and beam set is sometimes called a "stamp" and mills are sometimes categorised by how many stamp sets 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.

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

The Caledonia No. 1, Deadwood Terra No. 2, and Terra No. 3. Gold Stamp Mills, located at Terraville, SD. 1888

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.