Metate and mano from Custer County
Milling stones are common artifacts on many Oklahoma archaeological sites. The milling stone or milling basin, frequently called a metate, was used for grinding seeds, corn, or other vegetal products into a flour for food. Specimens are more frequent at sites after the appearance of agriculture and pottery although they also occur on older sites and probably were used for processing wild plant foods.
Milling stones are normally large flattened rocks of considerable weight which have a shallow or deep basin-shaped depression in one or both sides. They were used in conjunction with a hand stone or mano to grind seeds or grain. Whole specimens are less frequently found than broken fragments on archaeological sites.
The classification of milling stones or grinding basins is not standardized among writers, but some general suggestions can be made regarding variations in these artifacts. The term "metate" is derived from the Southwest and Mexico to refer to the corn grinding stone still available today in Mexican markets. This term has been commonly applied to all kinds of grinding basins found elsewhere even though obvious differences exist. One characteristic of the usage of the metate is the grinding process itself in which the hand stone is rubbed back and forth in a washboard motion to grind the grain. This movement results in a trough-shaped grinding surface which is best utilized with a long two-handed grinding stone that can be moved back and forth. The term metate is appropriate for a milling stone of this type (Figure l7a).
Most of the milling stones found in Oklahoma, however, have oval or circular-shaped grinding surfaces in which the hand stone was moved in a circular or rotary motion (Figure l7b). It is suggested that these be termed milling basins and that the term metate be restricted to the trough-shaped forms similar to those found in the Southwest.
Another term frequently used is "milling slab" (Figure l7c). This refers to a milling stone which is almost flat with a shallow or slightly depressed basin. These are characteristic of older sites such as the Archaic and were apparently used for grinding seeds or wild grains. The stone slab which has been used for this purpose is rarely altered except for preparation of the milling surface.
Metates, milling basins, and milling slabs are all found in Oklahoma. Metates tend to occur in the western portion of the state while the others are found in all locations.
The milling basins, as well as the metates, sometimes show considerable intentional shaping of the stone around the basin area. Shallow cups or pits are sometimes present along the ends or margins. The depth of the basin-shaped depression varies considerably depending upon the amount of grinding and use of the stone. The basin surface must be occasionally roughened by peck marks in order to have a suitable grinding surface and this deepens the basin area with continuous usage. Some specimens become broken by the pecking process or roughening as the basin becomes too deep for the thickness of the stone.