tama-ishi 玉石

Lit. "round stone." A boulder about 15-30 cm across, which has been naturally rounded by a river or ocean waves. Often andesite anzangan 安山岩 or granite kakōgan 花崗岩. Tama-ishi are used as paving stones *shiki-ishi 敷石 in gardens (see *tama-ishijiki 玉石敷, *nobedan 延段), for stone beaches ishihama 石浜, as base stones *soseki 礎石 supporting walls or pillars, in stone walls tsumi-ishi 積石, in front of a garden wash basin suimon 水門, and as kerb stones fuchi-ishi 縁石. Although ocean stones are rounder than river stones, the salt content of ocean stones prevents moss from growing on them.