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, 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 (4.7 inch) in diameter by 10 centimeters (3.9 inches) deep, although a considerable range of depths of the cavities have been documented .[ Discovering Prehistoric Sites: Objective and Subjective Survey Techniques, Daniel G. Foster, Brian D. Dillon, and Linda C. Sandelin, California Department of Forestry and Fire Protection, June 13, 2005] 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.
Bedrock metate
A bedrock mortar should not be confused with a bedrock
metate, which is a flat, trough-shaped depression often found with bedrock mortars.
Example locations of occurrence
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Southern Arizona: In the Santa Catalina, Santa Rita, Rincon Mountains, Sierrita, and Tucson Mountains, and also in rock outcroppings in the valleys
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Along the north banks of the middle reaches of the Merced River in Mariposa County, California, United States
[G. Deghi, J. Buxton et al., Earth Metrics, Environmental Impact Report for the Saxon Creek Water Project, Mariposa County, California, published by the County of Mariposa Planning Department and Mariposa County Water Agency, Report 10298, May, 1990]
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In Santa Barbara and San Luis Obispo counties on the California Central Coast
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In northern Mexico within the Sierra Tarahumara of Southern Chihuahua
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The Upper Cumberland Plateau of Tennessee, United States
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Inside many rock shelters in Menifee County, Kentucky, United States
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The Cueva de los Corrales region of northwestern Argentina
[M. Del Pilar Babot, MarĂa C. Apella, Maize and Bone: Residues of Grinding in Northwestern Argentina, Archaeometry, Volume 45 Issue 1 Page 121-132, February 2003]
Gallery
File:Garrod's terrace el-Wad.jpg|Natufian culture bedrock mortars at Mount Carmel, Israel.
File:Muidu bedrock mortars.jpg|Maidu people bedrock mortars in northern California.
File:AnzaMorterosByPhilKonstantin.jpg|Bedrock mortars at Anza-Borrego Desert State Park in southern California.
File:Acorn grinding stone-750px.jpg|Bedrock mortars used to grind in California.
File:Indian_Kitchen_Bedrock_Mortars_2013.jpg|Hohokam bedrock mortars at Indian Kitchen, Arizona.
File:Huerfano Butte Arizona Bedrock Mortars Number 1.jpg|Bedrock mortars at Huerfano Butte.
File:Huerfano_Butte_Arizona_Bedrock_Metate.jpg|A close up view of a bedrock metate at Huerfano Butte.
See also
Line note references