These beautiful silicaeous stones are dredged from the bed of the Red River in Dahua County, Guangxi Province, China. They are hard—6-7 on the Moh scale—and are often reddish-brown to golden-brown, sometimes streaked with black or gray or a greenish color. Dahua stones have been naturally polished by rapid flowing, silt laden waters. They were first introduced as viewing stones in the late 1990s and rapidly became popular, causing them to become expensive.