Bedrock mortar

Anthropogenic rock depression used for grinding

A bedrock mortar (BRM) is an anthropogenic circular depression in a rock outcrop or naturally occurring slab, used by people in the past for grinding of grain, acorns or other food products. There are often a cluster of a considerable number of such holes in proximity indicating that people gathered in groups to conduct food grinding in prehistoric cultures. Correspondingly the alternative name gossip stone is sometimes applied, indicating the social context of the food grinding activity. Typical dimensions of the circular indentations are approximately 12 centimeters in diameter by 10 centimeters deep, although a considerable range of depths of the cavities have been documented. The bedrock mortar has been identified in a number of world regions, but has been particularly intensely documented in the Americas. An alternative term for the bedrock mortar site is bedrock milling station.

This keyword could refer to multiple things. Here are some suggestions: