Pebble

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Sea wave polishing pebbles into rounded corners

Pebbles

For other uses, see Pebble (disambiguation).

A pebble is a clast of rock with a particle size of 4 to 64 millimeters based on the Krumbein phi scale of sedimentology. A rock made predominantly of pebbles is termed a conglomerate. Pebble tools are among the earliest known man-made artifacts, dating from the Palaeolithic period of human history. They have been found at Olduvai Gorge (1.85 million years ago^{[citation needed]}) and at Longuopo in China (1.8 to 1.5 MYA^{[citation needed]}).

A beach composed chiefly of surface pebbles is commonly termed a shingle beach, which has armoring characteristics with respect to wave erosion; moreover, this type of beach has unusual ecological niches that may provide habitat for a number of rare and endangered species.

See also

• Gravel

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