Tool sharpening grooves in a boulder.
Freezeout Canyon, Baca County,
Colorado. Photo: Peter Faris, 1996.
There are certain types of rock markings that really should not be called rock art. One of these is the tool sharpening groove. These are created by the act of sharpening a bone or antler-tine awl on the rock surface. As the tool is sharpened it also wears away the surface of the rock. As the point becomes sharper the groove it wears is also narrower, eventually becoming a “v-shaped” groove abraded into the rock. Another type of tool mark on the surface of the rock is a wider, shallow smoothed area that is created by sharpening the edge of a stone tool such as an axe. Many examples of these can be seen in the illustration of the site from the Picketwire Canyonlands. Another example often lumped in with rock art (or at least recorded with the rock art at a site) is the bedrock metate, a shallow hollow in a horizontal rock surface that was used for grinding plant materials with a hand held stone called a mano.
Tool sharpening grooves in cliff,
Picketwire Canyon, Bent County,
CO. Photo: Peter Faris, 1997.
Linea Sundstrom has pointed out that tool grooves can be helpful in roughly estimating dates. Tool sharpening grooves essentially ceased being made when trade with Anglos, whether European or American, began to trade goods for furs, because among early essential items for such trade were metal awls and needles. This suggests that any rock markings that can be identified as tool grooves were basically prehistoric. The presence of tool grooves also suggests either a habitation site or, at least, a site where preparations for domestic chores were conducted. I believe we got into the habit of including these indications of industrial practices in with rock art because when rock art is being recorded it is considered important to record all features on the surface of the rock, including tool grooves, axe sharpening hollows, and bedrock mutates.
Some examples can be found where tool-sharpening grooves have been incorporated into rock art images. I have seen tool sharpening grooves that had been turned into lizards by the addition of four legs paired on both sides of the groove by pecking or abrasion.
If the tool groove is somehow incorporated into a rock art image as in the lizards mentioned above, then I would classify the modified tool groove as rock art. If the tool groove, however, is not modified, or demonstrably incorporated into rock art elements, I will have to classify it as another element of the rock surface that needs to be recorded, but not as rock art.