The process of making Yunzi was lost in the 1920s when the Chinese Civil War spread to Yunnan province, but in the late 1960s it was rediscovered by the now state-managed Yunzi Company. The Yunzi company claims their stones have an advantage of a pleasant sound when placed on the board. Yunzi are delicately made with a jade-like luster yet are neither brittle nor slippery. The black and white pieces each have their special qualities. The white pieces are opaque with a tint of yellow or green. The black pieces are dark, and when held to the light a translucent green hue. With new technology, Yunzi stones can now be made pure white without any discolorations.