Value and Price

Hyuga Clam Shell
Mexican Clam Shell
Glass, ceramics, etc.
Plastics, etc.
Nachi-Kuroishi from Kumano City, Mie Prefecture
Other Domestic Black Stones
Foreign black stone
Glass, ceramics, etc.
Plastics, etc.
In the case of white Go stones made from clam shells, it is very difficult to produce Go stones without flaws or colors, because there are flaws originating from the material, or flaws are caused in the manufacturing process, or the color of the material remains. In addition, our Go stones have an ideal Go stone shape for each size. Any stones that deviate significantly from this ideal shape are excluded from our products. In the case of Nachiguro Black Go stones, there is no difference in quality compared to Clam White Go stones because there are no stripes and the quality of the material is stable.
Premium grade
Almost flawless Go stones
All of our Go stones, white and black, are selected by our craftsmen for quality. Go stones with almost no flaws are classified as "Selected" grade.
Blue label
Go stones with slight scratches and color remaining
Go stones that have been carefully selected but still have slight flaws and color are classified as "Blue Label" grade. Go stones that do not meet the Blue Label standards will not be commercialized.
Clamshell White Go Stones Stripe Rank
Snow grade
Top quality (approx. 5-10%)
The grade of Clamshell White Go Stone is ranked by the stripes of the Go Stone. Clamshell White Go stones have stripes on one side of the stone (some stones have a little stripe on the other side). The side with stripes is called "Omote" and the other side is called "Belly". The more stripes on a Clam White Go stone, the thinner the stripes themselves are and the straighter and narrower the distance between stripes, the more beautiful and valuable the Go stone is.
Blossom grade
Grade (stripe) is less than Snow grade
Only clamshell White Go stones with more than 80% of the total stripes are the highest grade "Snow grade". Because only about 5 to 10% of all clamshell White Go stones are produced, "Snow grade" is a very rare and relatively expensive clamshell White Go stone. Striped Go stones that do not meet the "Snow grade" grade are classified by quality as "Premium Blossom grade" for stones with almost no flaws, and "clamshell Go stones Blue Label" for stones that were not selected carefully but still have slight flaws and color.
Size (Thickness)
The thickness of Go stones (Clamshell White Go stones and Nachikuro Black Go stones) are standardized from size 20 to size 50. Clamshell white Go stones are made from natural clam shells, and since only a small number of thicker shells can be obtained, the thicker the Go stone, the more expensive it is. Normally, we sell 12 types of Clamshell Go stones in even numbers from size 28 (7.5mm) to size 50 (14.3mm).
The thickness and diameter of our Go stones are slightly different between white Go stones and black Go stones of the same size. The thickness of Nachikuro Black Go stones is 0.3mm thicker and the diameter is 0.3mm larger than Clamshell White Go stones of the same size.
The standard diameter of the Clam White Go Stone is 21.9 mm, while the diameter of the Nachi Black Go Stone is 22.2 mm.
The reason for this is that white is an expansion color, so when white and black stones of the same diameter and thickness are viewed by the human eye, the black stones appear slightly smaller, so they are adjusted to appear about the same size. If the black stones look smaller on the board, it would seem psychologically disadvantageous, so the stones are adjusted so that they appear to be about the same size to the human eye.