Stones tools were used extensively in prehistory to process plant foods and other materials. Grinding stones work through friction, reducing a material to powder between two stones.
Grinding stones were used to grind and crush different materials including seeds, bulbs, berries, insects, fibres, and ochre. In hand-grinding, the top stone was small enough to fit in the hand, and usually had a convex surface. The bottom stone was usually concave, and the concavity developed as the stone wore away through use. Grinding stones were usually made from course-grained, abrasive materials such as sandstone or basalt.
Archaeologists refer to grinding stone by different terms depending on the region. In the Americas, the bottom stone is often referred to as a metate, a Spanish term derived from the Nahuatl word metlatl, or ‘grinding stone’. The top stone is referred to as a mano, Spanish for ‘hand’. In Europe and West Asia, archaeologists refer to grinding stones as querns, from Old English cweorn, ‘hand-mill’. The bottom stone in hand-grinding is referred to as a saddle quern, and the top stone a muller, from Middle English mullen, ‘to grind’. The term muller is also used in Australia to refer to the top stone. Many archaeologists prefer to use the generic terms ‘top stone’ and ‘bottom stone’.