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A stamp mill (or stamp battery or stamping 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.


Description

A stamp mill consists of a set of heavy
steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistan ...
(
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
-shod
wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin ...
in some cases) 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 Shaft may refer to: Rotating machine elements * Shaft (mechanical engineering), a rotating machine element used to transmit power * Line shaft, a power transmission system * Drive shaft, a shaft for transferring torque * Axle, a shaft around whi ...
. 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. The California Stamp made its major debut at the 1894 San Francisco midsummer fair. It was the first type that generated electricity, powered by a wood feed steam boiler. Steam started the wheels and belts turning; a generator that also was steam driven supplied the electricity for overhead lighting. This was a big plus for mining company, enabling more production time.


History

The main components for water-powered stamp mills –
water wheel A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buckets ...
s, cams, and hammers – were known in the Hellenistic era in the
Eastern Mediterranean Eastern Mediterranean is a loose definition of the eastern approximate half, or third, of the Mediterranean Sea, often defined as the countries around the Levantine Sea. It typically embraces all of that sea's coastal zones, referring to commun ...
region. Ancient cams are in evidence in early water-powered automata from the third century BC. A passage in the '' Natural History'' of the
Roman Roman or Romans most often refers to: * Rome, the capital city of Italy * Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a lett ...
scholar Pliny (NH 18.23) indicates that water-driven pestles had become fairly widespread in Italy by the first century AD: "The greater part of Italy uses an unshod pestle and also wheels which water turns as it flows past, and a trip-hammer
ola Ola may refer to: Places Panama * Olá, a subdistrict in Coclé Province * Olá District Russia *Ola, Russia, an urban settlement in Magadan Oblast *Ola District, an administrative division in Magadan Oblast *Ola (river), a river in Magadan Ob ...
.Wilson, p.16. These trip-hammers were used for the pounding and hulling of
grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
. Grain-pounders with pestles, as well as ordinary watermills, are also attested as late as the middle of the fifth century in a
monastery A monastery is a building or complex of buildings comprising the domestic quarters and workplaces of monastics, monks or nuns, whether living in communities or alone (hermits). A monastery generally includes a place reserved for prayer whic ...
founded by Romanus of Condat in the remote Jura region, indicating that the knowledge of trip hammers continued into the early
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
. Apart from agricultural processing, archaeological evidence also strongly suggests the existence of trip hammers in Roman metal working. In Ickham in
Kent Kent is a county in South East England and one of the home counties. It borders Greater London to the north-west, Surrey to the west and East Sussex to the south-west, and Essex to the north across the estuary of the River Thames; it faces ...
, a large metal hammer-head with mechanical deformations was excavated in an area where several Roman water-mills and metal waste dumps have also been traced. The widest application of stamp mills, however, seems to have occurred in Roman mining, where ore from deep veins was first crushed into small pieces for further processing. Here, the regularity and spacing of large indentations on stone anvils indicate the use of cam-operated ore stamps, much like the devices of later
medieval In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...
mining.Barry C. Burnham: "Roman Mining at Dolaucothi: The Implications of the 1991-3 Excavations near the Carreg Pumsaint", ''Britannia'', Vol. 28 (1997), pp. 325-336 (333-335) Such mechanically deformed anvils have been found at numerous Roman silver and gold mining sites in
Western Europe Western Europe is the western region of Europe. The region's countries and territories vary depending on context. The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the ancient Mediterranean ...
, including at Dolaucothi (
Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...
), and on the
Iberian peninsula The Iberian Peninsula (), ** * Aragonese and Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a peninsula in southwestern Europe, def ...
, where the datable examples are from the 1st and 2nd century AD. At Dolaucothi, these stamp mills were hydraulic-driven and possibly also at other Roman mining sites, where the large scale use of the hushing and ground sluicing technique meant that large amounts of water were directly available for powering the machines.Wilson, pp. 21f. Stamp mills were used by miners in
Samarkand fa, سمرقند , native_name_lang = , settlement_type = City , image_skyline = , image_caption = Clockwise from the top:Registan square, Shah-i-Zinda necropolis, Bibi-Khanym Mosque, view inside Shah-i-Zinda, ...
as early as 973. They were used in medieval
Persia Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...
to crush mineral ores. By the 11th century, stamp mills were in widespread use throughout the medieval Islamic world, from Islamic Spain and North Africa in the west to
Central Asia Central Asia, also known as Middle Asia, is a region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes the fo ...
in the east. Water-powered and mechanised trip hammers reappeared in medieval Europe by the 12th century. Their use was described in medieval written sources of
Styria Styria (german: Steiermark ; Serbo-Croatian and sl, ; hu, Stájerország) is a state (''Bundesland'') in the southeast of Austria. With an area of , Styria is the second largest state of Austria, after Lower Austria. Styria is bordered ...
(in modern-day Austria), one from 1135, and another from 1175. Both texts mentioned the use of vertical stamp mills for ore-crushing. Medieval French sources of the years 1116 and 1249 both record the use of mechanised trip hammers used in the forging of
wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag inclusions (up to 2% by weight), which give it a wood-like "grain" ...
.Needham, p. 379. Medieval European trip hammers by the 15th century were most often in the shape of the vertical pestle stamp-mill. The well-known
Renaissance The Renaissance ( , ) , from , with the same meanings. is a period in European history marking the transition from the Middle Ages to modernity and covering the 15th and 16th centuries, characterized by an effort to revive and surpass ide ...
artist and inventor
Leonardo da Vinci Leonardo di ser Piero da Vinci (15 April 14522 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially rested on ...
often sketched trip hammers for use in forges and even file-cutting machinery, those of the vertical pestle stamp-mill type. The oldest depicted European illustration of a ''martinet'' forge-hammer is perhaps in the '' Historia de Gentibus Septentrionalibus'' of Olaus Magnus, dated to 1565 AD. This woodcut image depicts three martinets, and a waterwheel working the wood and leather bellows of an osmund ( sv)
bloomery A bloomery is a type of metallurgical furnace once used widely for smelting iron from its oxides. The bloomery was the earliest form of smelter capable of smelting iron. Bloomeries produce a porous mass of iron and slag called a ''bloom' ...
furnace. The recumbent trip hammer was first depicted in European artwork in an illustration by Sandrart and Zonca (dated 1621 AD). Water-powered stamp mills are illustrated in book 8 of
Georg Agricola Georgius Agricola (; born Georg Pawer or Georg Bauer; 24 March 1494 – 21 November 1555) was a German Humanist scholar, mineralogist and metallurgist. Born in the small town of Glauchau, in the Electorate of Saxony of the Holy Roman Empir ...
's '' De Re Metallica'', published in 1556. The mills Agricola shows were largely wooden construction, excepting the use of
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
shoes on the end of each stamp. The
camshaft A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...
was set directly on the axle of the waterwheel, and stamps were typically arranged in gangs of three, with each wheel driving one or two gangs.


19th century

The first stamp mill in the U.S. was built in 1829 at the Capps mine near
Charlotte, North Carolina Charlotte ( ) is the most populous city in the U.S. state of North Carolina. Located in the Piedmont region, it is the county seat of Mecklenburg County. The population was 874,579 at the 2020 census, making Charlotte the 16th-most popu ...
. They were common in
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
,
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
, and
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
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 Cornwall (; kw, Kernow ) is a Historic counties of England, historic county and Ceremonial counties of England, ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people ...
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 wheel A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buckets ...
s and larger ones by steam engines. Californian stamps were based on Cornish stamps and were used for the
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
n 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.


Other stamping mills

Stamp mills were used in early
paper making Papermaking is the manufacture of paper and cardboard, which are used widely for printing, writing, and packaging, among many other purposes. Today almost all paper is made using industrial machinery, while handmade paper survives as a speciali ...
for preparing the paper-stuff ( pulp), before the invention of the
Hollander beater A Hollander beater is a machine developed by the Dutch in 1680 to produce paper pulp from cellulose containing plant fibers. It replaced stamp mills for preparing pulp because the Hollander could produce in one day the same quantity of pulp it w ...
, and might have derived from those used in
fulling Fulling, also known as felting, tucking or walking ( Scots: ''waukin'', hence often spelled waulking in Scottish English), is a step in woollen clothmaking which involves the cleansing of woven or knitted cloth (particularly wool) to eli ...
wool. They were used in oil-seed processing prior to pressing the oil from the milled seeds. Early mills were water-powered but mills can also be steam or electric powered. A stamping mill may refer to a factory that performs stamping.


See also

*
Ball mill A ball mill is a type of grinder used to grind or blend materials for use in mineral dressing processes, paints, pyrotechnics, ceramics, and selective laser sintering. It works on the principle of impact and attrition: size reduction is done ...
- a horizontal cylinder containing metal balls to crush the material *
Hammermill A hammer mill is a mill whose purpose is to shred or crush aggregate material into smaller pieces by the repeated blows of little hammers. These machines have numerous industrial applications, including: * Ethanol plants (grains) * A farm mac ...
- a more modern device that also can crush material to fines. * Hammer mill - an historical forge using trip hammers * Stamp sand - the product of ore mills * Usu (Mortar) - a Japanese Stamp mill


References


Bibliography

*Needham, Joseph: Science and Civilization in China: Volume 4, Part 2. (Taipei: Caves Books Ltd 1986) * Wilson, Andrew (2002): "Machines, Power and the Ancient Economy", '' The Journal of Roman Studies'', Vol. 92, pp. 1–32 (16, 21f.)


External links


Paymaster Stamp Mill
near Lewiston, California
Paymaster Stamp Mill
relocated to Jake Jackson Museum, Weaverville, California
Kentucky Mine Stamp Mill
and museum, near Sierra City, 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 1900s.
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.
Superstition Mountain Museum 20-Stamp Mill
near
Apache Junction Apache Junction is a city in Pinal and Maricopa counties in the state of Arizona. As of the 2020 census, the population was 38,499, most of whom lived in Pinal County. It is named for the junction of the Apache Trail and Old West Highway. ...
,
Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
{{Extractive metallurgy Grinding mills Mining equipment