Milling and Grinding Tools

Native people in California traditionally used stone (and sometimes wood) for milling seeds, pulverizing small animals, grinding pigments, and other uses.  Wooden tools very rarely survive in the archaeological record, but stone tools remain for thousands of years.  The most common milling and grinding tools in California are the mortar and pestle, and the millingstone and handstone (also called by their Spanish names, metate and mano [“hand”]).  Sometimes these items are carefully and beautifully shaped, and sometimes they are unshaped, “expedient” tools that are recognizable only by the polish or wear on them.  Often they are found in pieces, rather than as whole implements, and so it is important to be able to recognize the fragments.

Millingstones or “Metates”

Millingstone fragments
Look carefully at these fragments of broken millingstones.  They can be difficult to recognize, but they should show some type of wear, in the form of smooth, polished areas; high spots that have been ground flat; a “dished” or slightly concave surface; or sometimes pecking to make the smoothed surface rough again to allow continuing use.  Sometimes a millingstone is also used as an anvil to crack open nuts and other hard items; in these cases, there will be small, circular pitted areas on the flat stone.

The two photos at left are of the same fragment and as you can see it is sometimes easier to see the smoothly ground surface in the end view.

Below are three photos of nearly complete millingstones.

Nearly complete millingstones

Handstones or “Manos”

Handstones are the smaller, hand-held stones used to grind the seeds or other materials against the millingstone.  They show similar kinds of wear, and sometimes have been used as pestles or hammerstones as well as handstones – in these cases, there are battered areas as well as smoothed areas on the tool.

Mortars

Mortars are deep, cup-shaped holes used for pounding and pulverizing various materials.  Often they are associated with acorn processing, but they were used for other things, as well.  Mortars occur as bowls shaped from stone or wood; or as cups formed in rocks, boulders, or bedrock outcroppings.  Sometimes natural holes in stone can be mistaken for mortars, but the natural ones are rarely as smooth and rounded as those made by humans.

Mortar

(Photo courtesy of Dan Foster)
Bowl mortar

Pestles

Pestles are generally elongated to fit into the mortar holes and one or sometimes both ends are battered. The ”business” end of a well-used pestle can be battered almost flat by contact with the stone mortar.

Other pestles are carefully shaped, like the basalt specimens you see here.
This unusual pestle, made from very fine-grained basalt, has a nipple-shaped end rather than a flat end.  This means that the material of the mortar was softer than the basalt of the pestle, and so did not cause the heavy battering seen in other pestles.  This item was most likely used in a wooden mortar, rather than a stone one.
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