Nachiguro: The Black Stone Behind Japan’s Finest Go Sets

If you have ever looked at a Japanese go set listed as “hamaguri and nachiguro”, you have seen the classic pairing: white stones cut from clamshell (hamaguri) and black stones cut from a natural black slate called nachiguro (那智黒).

The white stones get most of the attention, because their grade and thickness drive the price. But the black stones are a different material, from a different place, made by different craftspeople. This page explains what nachiguro is, why it is prized, and what to check before you buy.

The short version

• Nachiguro is a hard black natural stone from Kumano City (Kamikawa-cho), Mie Prefecture. Despite the name, it does not come from the Nachi area of Wakayama.
• It is valued for a deep, even black and a soft sheen after polishing.
• The classic high-end set is nachiguro blacks with clamshell whites, matched by size number.
• The word “nachiguro” on a listing is not proof of origin. Ask the shop what the stone is and where it comes from.
• Black stones are not graded “yuki / tsuki / hana” the way clamshell whites are. Their value comes from the stone, the polishing and the thickness.

What nachiguro is

Nachiguro is a black, fine-grained stone quarried around Kamikawa-cho in Kumano City, Mie Prefecture. Beyond go stones, it has long been used for inkstones and ornaments. The “Nachi” in the name refers to the famous Nachi area in neighbouring Wakayama, but the stone itself is a Mie product — a common mix-up even in Japanese listings.

In a Japanese set, white and black are two separate crafts. White stones are cut from shell; black stones are cut and polished from rock. That is why it usually makes sense to choose the white stones first, and then match black stones of the same size number.

Why it is prized

Colour and sheen. Good nachiguro is a deep black with little blue or grey cast, and takes a quiet, soft gloss when polished. Cheaper black stones can look slightly bluish or greyish beside it.

Feel in the hand. A natural hard stone has a weight and a cool, smooth touch that glass and plastic stones do not. Many players notice it the first time they take a stone from the bowl.

The contrast with clamshell. On a kaya board, nachiguro blacks and clamshell whites give the high contrast that people associate with a “proper” Japanese set.

Natural stone also varies slightly from stone to stone. That is not a defect; it is what natural material looks like. If you want every stone to look identical, glass or resin is the better choice.

Does black come in grades?

Not in the way white does. Clamshell whites are graded by their stripe pattern — yuki, tsuki, hana — and that grade can change the price many times over (see Clamshell stone grades). Black stones are not usually sold under those labels. What you compare is:

To be honest about the limits: telling the material from a photo alone is hard even for experienced buyers. The reliable route is a shop that states the origin and material and will answer questions before you order.

Matching blacks to whites

Size numbers describe thickness, not diameter. According to the Nihon Ki-in, the standard diameter is 21.9 mm for white and 22.2 mm for black: black stones are made about 0.3 mm larger on purpose, because white looks bigger to the eye. A full set is 180 white and 181 black stones, 361 in total.

When you buy, pair blacks and whites of the same size number, and choose bowls that hold that size (see Choosing go bowls). For how size numbers relate to thickness, see Go stone sizes, and for the overall approach, Choosing go stones.

For a sense of scale: at the Osaka shop Syogoya’s official online store, hard glass stones (stones only) started at about 5,280 yen, clamshell size 30 in the economy grade was 18,150 yen, and a certified “yuki” grade clamshell set reached 308,000 yen (prices including Japanese tax, excluding international shipping; checked 8 October 2026 — Syogoya glass and resin stones, Syogoya clamshell stones). Most of that spread comes from the white stones, which is why the choice of white usually comes first.

Caring for nachiguro

Nachiguro is hard, but its polish is not indestructible.

• Wipe with a soft dry cloth after play.
• Do not scrub with abrasives or melamine sponges; the gloss will become patchy.
• Avoid strong cleaning chemicals.
• If the black looks whitish or dull, the surface has dried out. Kuroki Goishiten notes that its black stones are finished with oil, and advises wiping them with a cloth lightly moistened with baby oil or a low-odour, non-sticky natural oil to bring the gloss back (Kuroki Goishiten: caring for go stones, checked 8 October 2026).
• Keep the stones dry and out of direct sunlight, and wipe them before putting them back in the bowls.

FAQ

What is nachiguro? A hard black natural stone from Kumano City in Mie Prefecture, Japan, used for the black stones in high-end go sets. It is valued for its deep black colour and soft sheen.

Is nachiguro from Nachi in Wakayama? No. The name borrows “Nachi”, but the stone is from Kamikawa-cho, Kumano City, Mie Prefecture.

How can I tell real nachiguro? Look at colour, sheen, weight and price together, and ask the shop to state the material and origin. Judging from appearance alone is difficult; buying from a shop that names the origin is the dependable route.

Do black stones have grades like clamshell? Not usually. The yuki / tsuki / hana grades are for clamshell whites. Black stones are compared by material, polish and size number.

Should I buy whites and blacks together? Yes, ideally as a matched set of the same size number. Clamshell whites with nachiguro blacks at the same size number is the classic combination.

This page summarises general knowledge about nachiguro go stones (checked 7 October 2026). Origin, material and price differ by product; confirm them with the shop before you buy. Kayajudo is an independent information site about go and shogi equipment.