The grinders and mortars are frequently found composed of softer rock,
either ferruginous sandstone or gritty clays. For a more complete
knowledge of these stone implements we must depend on a comparative
study of large collections from different localities, and such
information as the circumstances attending their discovery may impart,
rather than upon their present condition or the uses for which they are
now employed.

Metates or grain-grinders, pestles and rubbing stones belong to the
milling industry among the Indians. The metates are generally quite
large and heavy, and could not well be transported with the limited
means at the command of Indians. They are therefore well adapted to the
uses of village Indians, who remain permanently in a place and prosecute
agricultural pursuits. They are generally of rectangular shape, and from
10 to 20 inches in length by 6 to 12 in width, and are composed of
various kinds of rock, the harder, coarse-grained kinds being
preferable, though in some instances sandstone is employed; the most
desirable stone is porous lava. These stones are sometimes carried with
families of the Pueblos moving short distances to the valleys of streams
in which they have farms in cultivation. In the permanent villages they
are arranged in small rectangular bins (see Fig. 508), each about 20
inches wide and deep, the whole series ranging from 5 to 10 feet in
length, according to the number of bins or divisions. The walls are
usually of sandstone. In each compartment one of these metates or
grinding stones is firmly set at a proper angle to make it convenient to
the kneeling female grinder. In this arrangement of the slabs those of
different degrees of texture are so placed as to produce an increased
degree of fineness to the meal or flour as it is passed from one to the
other. But a small number of these slabs were collected on account of