The Probert Encyclopaedia of General Information

MILLSTONE

A millstone is one of a pair of circular stones that are used for grinding grain or other substances. The surface of a millstone usually has a series of radial grooves in which the powdered material collects, and the stones are generally buhrstone or some kind of lava, such as Niedermendig, or another other firm rock with rough texture. Milling grain with stones introduces small quantities of stone into the flour, and this helps to accelerate the rate at which the teeth of consumers of such flour are worn away.
Research Millstone