Sado, the sixth largest island in Japan, lies off the coast of Niigata. In past times, it was a place of exile and gold mines. Worthy of note is the red chert, known locally as akadama, rock found there, which is one of the more important and widely collected stones in Japanese stone appreciation culture. Small to medium-sized stones are used as suiseki, while larger Sado Island akadama stones are sometime used as garden stones.