A flat circular stone, mounted on a spindle, and turned by a winch handle, used for the purpose of grinding edge tools. In districts where cutlery and edge tools are manufactured, great numbers of these stones are used in one building, called a blade mill or grind mill. The stone suited to form grindstones is composed of a coarse species of sandstone. The finer sorts of grindstones, and what are called whitening or polishing stones, by the Sheffield cutlers, are from different rocks in the upper part of the great Derbyshire Coal Series; others are from Staffordshire, Warwickshire, etc.