The white stones are made of a kind of white shell; they are highly polished, and are exceedingly pleasant to the touch. The best come from the provinces of Hitachi and Mikawa. The black are made of stone, generally a kind of slate that comes from the Nachi cataract in Kishiu. As they are used they become almost jet-black, and they are also pleasant to the touch, but not so much so as the white. A good set is quite dear, and cannot be purchased under several yen. The ideograph formerly used for “Go ishi” indicates that originally they were made of wood, and not of stone, and the old Chinese ideograph shows that in that country they were wooden pieces painted black and white. The use of polished shell for the white stones was first introduced in the Ashikaga period.
In form the stones are disk-shaped, but not always exactly round, and are convex on both surfaces, so that they tremble slightly when placed on the board. They are about three-quarters of an inch in diameter, and about one-eighth of an inch in thickness. The white stones are generally a trifle larger than the black ones; for some strange reason those of both colors are a little bit wider than they should be in order to fit the board. Korschelt carefully measured the stones which he used, and found that the black were seventeen-sixteenths of the distance between the vertical lines on his board, and about eighteen-nineteenths of the distance between the horizontal lines, while the white stones were thirteen-twelfths of the distance between the vertical lines and thirty-six thirty-sevenths of the distance between the horizontal lines. I found about the same relation of size in the board and stones which I use.