Millstones or mill stones are stones used in
gristmill
A gristmill (also: grist mill, corn mill, flour mill, feed mill or feedmill) grinds cereal grain into flour and Wheat middlings, middlings. The term can refer to either the Mill (grinding), grinding mechanism or the building that holds it. Grist i ...
s, for grinding
wheat
Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
or other grains. They are sometimes referred to as grindstones or grinding stones.
Millstones come in pairs: a
convex
Convex or convexity may refer to:
Science and technology
* Convex lens, in optics
Mathematics
* Convex set, containing the whole line segment that joins points
** Convex polygon, a polygon which encloses a convex set of points
** Convex polytope ...
stationary base known as the ''bedstone'' and a
concave
Concave or concavity may refer to:
Science and technology
* Concave lens
* Concave mirror
Mathematics
* Concave function, the negative of a convex function
* Concave polygon, a polygon which is not convex
* Concave set
* The concavity
In ca ...
''runner stone'' that rotates. The movement of the runner on top of the bedstone creates a "scissoring" action that grinds grain trapped between the stones. Millstones are constructed so that their shape and configuration help to channel ground flour to the outer edges of the mechanism for collection.
The runner stone is supported by a cross-shaped metal piece (
millrind
A millrind or simply rind is an iron support, usually four-armed or cross-shaped, for the upper ("runner") stone in a pair of millstones.
The rind is affixed to the top of the square-section main shaft or spindle and supports the entire weight o ...
or rynd) fixed to a "mace head" topping the main shaft or spindle leading to the driving mechanism of the mill (
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
,
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
(including
tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide t ...
) or other means).
History
![Holgate Windmill millstones - 2011-12-26](https://upload.wikimedia.org/wikipedia/commons/5/57/Holgate_Windmill_millstones_-_2011-12-26.jpg)
The earliest evidence for stones used to grind food is found in northern Australia, at the
Madjedbebe
Madjedbebe (formerly known as Malakunanja II) is a sandstone rock shelter in Arnhem Land, in the Northern Territory of Australia, said to be the site of the oldest evidence of human habitation in the country. It is located about from the ...
rock shelter in
Arnhem Land
Arnhem Land is a historical region of the Northern Territory of Australia, with the term still in use. It is located in the north-eastern corner of the territory and is around from the territory capital, Darwin. In 1623, Dutch East India Compan ...
, dating back around 60,000 years. Grinding stones or grindstones, as they were called, were used by the
Aboriginal peoples
Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...
across the continent and islands, and they were traded in areas where suitable sandstone was not available in abundance. Different stones were adapted for grinding different things and varied according to location. One important use was for foods, in particular to grind seeds to make bread, but stones were also adapted for grinding specific types of starchy nuts,
ochre
Ochre ( ; , ), or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced ...
s for artwork, plant fibres for string, or plants for use in
bush medicine, and are still used today. The Australian grindstones usually comprise a large flat sandstone rock (for its abrasive qualities), used with a top stone, known as a "muller", "pounder",
or
pestle
Mortar and pestle is a set of two simple tools used from the Stone Age to the present day to prepare ingredients or substances by crushing and grinding them into a fine paste or powder in the kitchen, laboratory, and pharmacy. The ''mortar'' () ...
. The
Aboriginal peoples of the present state of Victoria used grinding stones to crush roots, bulbs, tubers and berries, as well as insects, small mammals and reptiles before cooking them.
Neolithic
The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several parts ...
and
Upper Paleolithic
The Upper Paleolithic (or Upper Palaeolithic) is the third and last subdivision of the Paleolithic or Old Stone Age. Very broadly, it dates to between 50,000 and 12,000 years ago (the beginning of the Holocene), according to some theories coin ...
people in Europe used millstones to grind
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 ...
s, nuts,
rhizomes
In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
and other vegetable food products for consumption.
These implements are often called grinding stones, and used either
saddle stones or rotary
quern
Quern ( da, Kværn) is a former municipality in the district of Schleswig-Flensburg, in Schleswig-Holstein, Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populo ...
s turned by hand. Such devices were also used to grind pigments and metal ores prior to
smelting
Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a ch ...
.
In India, grinding stones (''Chakki'') were used to grind grains and spices. These consist of a stationary stone cylinder upon which a smaller stone cylinder rotates. Smaller ones, for household use, were operated by two people. Larger ones, for community or commercial use, used livestock to rotate the upper cylinder. Today a majority of the stone flour mills (Atta Chakki) are equipped with lower stone rotating and upper stone stationary millstones also called Shikhar Emery Stones which are made from abrasive emery grains and grits, with a binding agent similar to Sorel Cement. These stones are made from two types of emery abrasives - Natural Jaspar Red Emery or Synthetic Calcined Bauxite Black Emery.
Millstones were introduced to Britain by the Romans during the 1st century AD and were widely used there from the 3rd century AD onwards.
Material
The type of stone most suitable for making millstones is a
siliceous rock
Siliceous rocks are sedimentary rocks that have silica (SiO2) as the principal constituent. The most common siliceous rock is chert; other types include diatomite. They commonly form from silica-secreting organisms such as radiolarians, diatoms
...
called
burrstone (or buhrstone), an open-textured, porous but tough, fine-grained
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
, or a silicified, fossiliferous
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
. In some sandstones, the cement is
calcareous
Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.
In zoology
''Calcareous'' is used as an adje ...
.
Millstones used in Britain were of several types:
*
Derbyshire
Derbyshire ( ) is a ceremonial county in the East Midlands, England. It includes much of the Peak District National Park, the southern end of the Pennine range of hills and part of the National Forest. It borders Greater Manchester to the nor ...
Peak stones of grey
Millstone Grit, cut from one piece, used for grinding
barley
Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...
;
[ imitation Derbyshire Peak stones are used as decorative signposts at the boundaries of the ]Peak District National Park Peak or The Peak may refer to:
Basic meanings Geology
* Mountain peak
** Pyramidal peak, a mountaintop that has been sculpted by erosion to form a point Mathematics
* Peak hour or rush hour, in traffic congestion
* Peak (geometry), an (''n''-3)-di ...
. Derbyshire Peak stones wear quickly and are typically used to grind animal feed since they leave stone powder in the flour, making it undesirable for human consumption.
* French buhrstones, used for finer grinding. French Burr comes from the Marne Valley
Val-de-Marne (, "Vale of the Marne") is a department of France located in the Île-de-France region. Named after the river Marne, it is situated in the Grand Paris metropolis to the southeast of the City of Paris. In 2019, Val-de-Marne had a p ...
in northern France. The millstones are not cut from one piece, but built up from sections of quartz cemented together, backed with plaster
Plaster is a building material used for the protective or decorative coating of walls and ceilings and for Molding (decorative), moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of ...
and bound with shrink-fit iron bands. Slots in the bands provide attachments for lifting. In southern England the material was imported as pieces of rock, only assembled into complete millstones in local workshops. It was necessary to balance the completed runner stone with lead weights applied to the lighter side.[
*Composite stones, built up from pieces of emery, were introduced during the nineteenth century; they were found to be more suitable for grinding at the higher speeds available when auxiliary engines were adopted.]
In Europe, a further type of millstone was used. These were uncommon in Britain, but not unknown:
* Cullen stones (stones from Cologne
Cologne ( ; german: Köln ; ksh, Kölle ) is the largest city of the German western States of Germany, state of North Rhine-Westphalia (NRW) and the List of cities in Germany by population, fourth-most populous city of Germany with 1.1 m ...
), a form of black lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
quarried in the Rhine Valley
), Surselva, Graubünden, Switzerland
, source1_coordinates=
, source1_elevation =
, source2 = Rein Posteriur/Hinterrhein
, source2_location = Paradies Glacier, Graubünden, Switzerland
, source2_coordinates=
, source ...
at Mayen
Mayen is a town in the Mayen-Koblenz District of the Rhineland-Palatinate Federal State of Germany, in the eastern part of the Volcanic Eifel Region. As well as the main town, additional settlements include Alzheim, Kürrenberg, Hausen-Betzing, ...
near Cologne, Germany.
* Lava stones from Orvieto (Italy), Mount Etna and Hyblaean Mounts (Sicily), and Pantelleria island, were used by the Romans.
Patterning
The surface of a millstone is divided by deep grooves called ''furrows'' into separate flat areas called ''lands''. Spreading away from the furrows are smaller grooves called ''feathering'' or ''cracking''. The grooves provide a cutting edge and help to channel the ground flour out from the stones.
The furrows and lands are arranged in repeating patterns called ''harps''. A typical millstone will have six, eight or ten harps. The pattern of harps is repeated on the face of each stone, when they are laid face to face the patterns mesh in a kind of "scissoring" motion creating the cutting or grinding function of the stones. When in regular use stones need to be ''dressed'' periodically, that is, re-cut to keep the cutting surfaces sharp.
Millstones need to be evenly balanced, and achieving the correct separation of the stones is crucial to producing good quality flour. The experienced miller will be able to adjust their separation very accurately.
Grinding with millstones
Grain is fed by gravity from the hopper into the feed-shoe. The shoe is agitated by a shoe handle running against an agitator (''damsel'') on the stone ''spindle'', the shaft powering the runner stone. This mechanism regulates the feed of grain to the millstones by making the feed dependent on the speed of the runner stone. From the feed shoe the grain falls through the ''eye'', the central hole, of the runner stone and is taken between the runner and the bed stone to be ground. The flour exits from between the stones from the side. The stone casing prevents the flour from falling on the floor, instead it is taken to the ''meal spout'' from where it can be bagged or processed further.
The runner stone is supported by the rind, a cross-
shaped metal piece, on the spindle. The spindle is carried by the ''tentering gear'', a set of beams forming a lever system, or a screw jack
A jackscrew, or screw jack, is a type of jack that is operated by turning a leadscrew. It is commonly used to lift moderately and heavy weights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable sup ...
, with which the runner stone can be lifted or lowered slightly and the gap between the stones adjusted. The weight of the runner stone is significant (up to ) and it is this weight combined with the cutting action from the porous stone and the patterning that causes the milling process.
Millstones for some water-powered mills (such as Peirce Mill
The Peirce Mill is a historic mill building located in Rock Creek Park, at Tilden Street and Beach Drive, Northwest, Washington, D.C., United States.
History
Issac Peirce, a millwright,NPS publication "Peirce Mill" GPO: 2004--304-337/00145 Repri ...
) spin at about 125 rpm.[NPS publication "Peirce Mill" GPO: 2004--304-337/00145 Reprint 2004]
Especially in the case of wind-powered mills the turning speed can be irregular. Higher speed means more grain is fed to the stones by the feed-shoe, and grain exits the stones more quickly because of their faster turning speed. The miller has to reduce the gap between the stones so more weight of the runner presses down on the grain and the grinding action is increased to prevent the grain being ground too coarsely. It has the added benefit of increasing the load on the mill and so slowing it down. In the reverse case the miller may have to raise the runner stone if the grain is milled too thoroughly making it unsuitable for baking. In any case the stones should never touch during milling as this would cause them to wear down rapidly. The process of lowering and raising the runner stone is called tentering and lightering. In many windmills it is automated by adding a centrifugal governor
A centrifugal governor is a specific type of governor with a feedback system that controls the speed of an engine by regulating the flow of fuel or working fluid, so as to maintain a near-constant speed. It uses the principle of proportional con ...
to the tentering gear.
Depending on the type of grain to be milled and the power available the miller may adjust the feed of grain to stones beforehand by changing the amount of agitation of the feed-shoe or adjusting the size of the hopper outlet.
Milling by millstones is a one-step process in contrast with roller mills in modern mass production where milling takes place in many steps. It produces wholemeal flour which can be turned into white flour by sifting to remove the bran.
Symbolism
In the Bible, the millstone is proverbial, designating something of great weight, for example in Matthew 18
Chapter 18 of the Gospel of Matthew contains the fourth of the five Discourses of Matthew, also called the ''Discourse on the Church'' or the ''ecclesiastical discourse''. It compares "the greatest in the Kingdom of Heaven" to a child, and also ...
:6
In heraldry
Heraldry is a discipline relating to the design, display and study of armorial bearings (known as armory), as well as related disciplines, such as vexillology, together with the study of ceremony, rank and pedigree. Armory, the best-known branch ...
, as a demonstration of military bravado, a millstone features as the heraldic crest of John de Lisle, 2nd Baron Lisle (c.1318-1355), one of the founder knights of the Order of the Garter
The Most Noble Order of the Garter is an order of chivalry founded by Edward III of England in 1348. It is the most senior order of knighthood in the British honours system, outranked in precedence only by the Victoria Cross and the George C ...
, as shown on his garter-plate in St George's Chapel, Windsor: ''A mill-stone argent pecked sable the inner circle and the rim of the second the fer-de-moline or''. Thus symbolising super-human strength necessary to support such a weight atop his helmet.
In its more basic heraldic form it is a charge
Charge or charged may refer to:
Arts, entertainment, and media Films
* '' Charge, Zero Emissions/Maximum Speed'', a 2011 documentary
Music
* ''Charge'' (David Ford album)
* ''Charge'' (Machel Montano album)
* ''Charge!!'', an album by The Aqu ...
symbolising industry.Bernhard Peter: The mill iron and derived forms
(in German) The ''fer-de-moline'' ("mill-iron") or millrind, which attaches to the millstone and transfers to it the torque of the drive-shaft, is also a common heraldic charge, used as canting arms
Canting arms are heraldic bearings that represent the bearer's name (or, less often, some attribute or function) in a visual pun or rebus.
French heralds used the term (), as they would sound out the name of the armiger. Many armorial all ...
by families named Mills, Milles, Turner, etc.
File:Höör vapen.svg, upright=0.5, A millstone in the arms of Höör
Höör (formerly spelled Hör, , old da, Hør) is a locality and the seat of Höör Municipality, Skåne County, Sweden with 7,865 inhabitants in 2010.
Name
The town was previously known as Hørg (in the 12th century), Hørgh (in the 15th ce ...
, Sweden
File:Askola.vaakuna.svg, upright=0.5, A millstone in the arms of Askola
Askola () is a municipality of Finland. It is located in the Uusimaa region. The municipality has a population of () and covers an area of of which is water. The population density is . Monninkylä is the largest village of municipality i ...
, Finland
See also
* Bedrock mortar
A bedrock mortar (BRM) is an anthropogenic circular depression in a rock outcrop or naturally occurring slab, used by people in the past for grinding of grain, acorns or other food products. There are often a cluster of a considerable number of ...
* Edge mill
An edge mill is a mill used for crushing or grinding in which stones roll around on their edges on a level circular bed. They were developed in China in the third century and are still used today in remote villages around the world. When the mill ...
* Quern-stone
Quern-stones are stone tools for hand- grinding a wide variety of materials. They are used in pairs. The lower stationary stone of early examples is called a saddle quern, while the upper mobile stone is called a muller, rubber or handstone. The ...
* Mühlsteinbrüche
The Mühlsteinbrüche ("Millstone Quarries") south of Jonsdorf in the Zittau Mountains in Saxony are a region of bizarre rock formations, which have been formed by the quarrying of sandstone for millstones and also by weathering processes. They a ...
, historic millstone quarries in Saxony
References
External links
{{commons category, Millstones
Millstone Dressing Tools
Video clip demonstrating millstone dressing
Millstones & Querns on Flickr
Grinding and lapping
Grinding mills
Food grinding tools
Stone objects
Heraldic charges