Millstone

millstone

Either of two flat, round stones used for grinding grain to make flour. The stationary bottom stone is carved with shallow grooved channels that radiate from the centre. The upper stone rotates horizontally, and has a central hole through which grain is poured. The channels of the bottom stone lead the grain onto the flat grinding section, called the land, and to the edge, where it emerges as flour. The best millstones are made from French buhrstone, quarried near Paris. In the U.S., quartz conglomerate, quartzite, sandstone, or granite is used. Stone-ground flour accounts for only a small proportion of milled flour today.

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millstone

one of a pair of heavy flat disc-shaped stones that are rotated one against the other to grind grain

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millstone [′mil‚stōn]

(petrology)

buhrstone

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Millstone 

a round, dressed natural or artificial stone; the working part of a set of millstones, which hulls glumaceous crops and mills grain and other materials. Millstones working in pairs were widespread in the third and fourth centuries B.C.; prior to that grain was ground in mortars. Millstones were originally turned by humans or animals, but when they became larger in size they came to be powered by water and wind.

Millstones are made of one or several pieces (natural) or small particles (artificial) of rock. Hard types of rock such as quartzite (the best), sandstone, and granite are used for natural millstones; artificial millstones are made of crushed flint, quartzite, and emery or a mixture of emery and flint, cemented together by magnesium chloride or caustic magne-site. On their working surfaces millstones have grooves, the edges of which are the cutting parts. Millstones with sharp edges split grain particles more rapidly.

A. IA. SOKOLOV