Yunzi Go Game Double Convex Stones - 9.2mm (Size 33)
Yunzi Go Stones - 9.2mm thick and a standard 21mm wide, double convex.   Yunzi stones have been made for almost a thousand years in the same area of Yunnan Province in southern China.  The secret recipe for making them is closely guarded, and nobody outside of Yunnan knows for sure what they're made of - although rumor has it that the ingredients include agate and Yunnan mountain stone mixed with agate. To make sure that stones are genuine, hold them up to the light and you will see a greenish halo form around the edge. This is a unique characteristic of Yunzi. The texture, symmetry, and   precision of these Go sets is captivating and sublimely captures the essence of the game.