pebble is a clast of rock with a particle size of 2 to 64 millimetres based on the Krumbein phi scale of sedimentology. Pebbles are generally considered larger than granules (2 to 4 millimetres diameter) and smaller than cobbles (64 to 256 millimetres diameter). 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.
Generally used as accessories in fountains, roadside coverings, gardens. They carry a tumbled finish, and are available in a variety of sizes - 5cm x 5cm x 3cm, 15cm x 15cm x 8cm, 30cm x 30cm x 15cm, and colors - white, grey, brown.