Yunzi

Yunzi (Traditional: 雲子; Simplified: 云子; Pinyin: Yúnzǐ) refer to special weiqi (Go) pieces manufactured in the Chinese province of Yunnan. At various times in history they have also been termed yunbian (云扁) and yunyaozi (云窑子). Though technically Yunzi refers only to sintered stones made of "yunzi" material (the exact composition is a secret), the term can also sometimes connote stones which are single-convex of any material. Yunzi-style stones made of jade for instance, were often presented to the reigning emperor and his court in ancient China.

Yunzi are delicately made with a green luster yet are neither brittle nor slippery. The black and white pieces each have unique individual qualities. Old style white pieces are opaque with a tint of yellow or green. The black pieces are dark, and when held to the light have a translucent green hue. Newer yunzi, however, have pure white stones.

The production of yunzi started in the Tang dynasty and reached its peak in the Ming and Qing dynasties; the total verifiable history of yunzi spans at least five hundred years.

Among yunzi, most famous was the yongzi (永子) manufactured by Yongchang Fu (永昌府, today the city of Baoshan, Yunnan) during the Ming dynasty. It was said that after a fire broke out in an imperial treasury, one of the keepers, who was from Yongchang Fu, discovered that melted pearls and jade had a special luster. When he returned to his hometown, he fashioned yunzi out of the agate and amber for which Yongchang Fu was famous. These yunzi went on to be prized by the literati and were offered to the Emperor.

Yunzi also appeared frequently in Chinese literature as the subject of a number of verses penned over the years, being mentioned in works such as Ming Yi Tong Zhi (Ming Dynasty Comprehensive Geographic Survey) and Travels of Xu Xiake, both of which favored the yongzi.

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