Amateur Naturalist: Eroded Rock, Grinding Stone, Or Sacred Stone?

Los Alamos

Rocks of all shapes and sizes can seen while exploring the slopes of the Jemez Mountains. But some create puzzles when looked at closely.

Consider a slope rising gently through a wooded landscape toward a mountain peak. The trees are spread apart and the grass is short as a result of the shade.

It is easy to see relatively small boulders that are two to three feet across, have relatively flat surfaces and are grey in color. A different appearing boulder then appears, (Picture A).

Picture A: How did this pattern of holes develop in the boulder? Photo by Robert Dryja

This particular boulder has the same coloration and surface texture as similar sized ones in the area. However it is somewhat squarish and has nine circular holes in it. Eight of the holes form a perimeter around the boulder. The ninth circular hole appears to be a drain leading out of the bottom.

Two sets of the holes form straight lines. A third set of holes continue around the perimeter. The holes forming the two straight lines are either about two inches or four inches in diameter. Even more unusual is a large square hole is at its center. Each of its sides is about 18 to 21 inches long.

How did this boulder develop this unusual set of holes? One possibility is that these are simply the result of erosion over the millennia. Indeed, other boulders in the area have holes but these vary in size and shape, (Picture B).

Picture B: A boulder with of holes of different shapes and sizes, suggesting natural erosion. Photo by Robert Dryja

Their random shape suggests they are the result of erosion. The unusual looking boulder may simply be the result of erosion as well—unusual but still the result of natural erosion. Three nearby smaller rocks suggest something else. They each have single hole on their top side that is about four inches in diameter.

One rock in particular appears worn at the bottom of its hole, as if it had been ground down, (Picture C).

Picture C: A rock with a circular hole toward its center and a smooth bottom. Photo by Robert Dryja

These may be grinding stones used to pulverize seeds or roots by paleo Indians. The boulder with multiple perimeter holes is different with its several holes. However a type of rock called a bedrock grinding stone can be seen in southern New Mexico and Arizona. Bedrock grinding stones have multiple holes.

The rectangular hole at the center of the boulder remains a puzzle. What was its purpose if made by paleo Indians? The rocks with a single circular hole suggest a third possibility. Rather than used for grinding food, the boulder may have been a sacred stone for the paleo Indians. This seems more plausible than carrying seeds and roots up a mountain slope to be ground.

A boulder with a similar pattern of holes was identified in 1915 elsewhere in the Jemez Mountains, possibly as part of a shrine.  It also has nine holes in it. Several of the mountain tops of the Valles Caldera in the Jemez Mountains are sacred sites and this boulder is toward a mountain top.

And so three options remain. Is the shape of the boulder the result of erosion; meant for grinding food; or to express sacred beliefs?

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