Nachi black stone

The geography of Nachiguroishi is exact. Its extraction is tied to Kamikawa-cho in Kumano City, and Kariya Baikando stands in Kamikawa-cho Kounoue. The name gathers a material, a narrow district, and working addresses in the same part of Kumano.

Kounoue returns in the Meiji-era account of wider sale. Yamanishi Tokunosuke of Kamikawa-cho Kounoue is linked with making and selling Nachiguroishi inkstones. The place name therefore attaches to extraction and to objects made for ink, paperweights, game pieces, and small polished forms.

Nachiguroishi is black, fine-grained, dense mudstone; geologically, it is also understood as black siliceous shale. Its color comes from material formation: carbon-rich aqueous slate came into contact with erupted lava, forming a fine black rock.

At the particle scale, Nachiguroishi is made from black opaque clastic material with particles around 0.1 micron. That fineness helps explain the surface: an inkstone made from Nachiguroishi takes time to grind ink, and polished objects depend on repeated sanding and finishing to bring out the dark sheen.

Black Go stones are one of Nachiguroishi’s clearest uses. Kumano City connects black Go stones with Nachiguroishi and notes that white stones are made from clam shell. On the board, the Kumano stone enters a small object used by hand.

Inkstones bring the same material to calligraphy. Nachiguroishi inkstones are fine and smooth, so grinding ink takes time; the finished ink is smooth and has been appreciated by literary users. Kariya Baikando also presents touchstones for checking gold purity, placing the stone across writing, games, and metal testing.

The history of Nachiguroishi moves through interruption and adaptation. The name appears in the 1839 Kii Zoku Fudoki; collection was once prohibited during the domain-government period, and after the ban was lifted in the mid-Meiji period, the stone was used for inkstones and paperweights.

Natural Nachiguroishi tends to split in plates, which made three-dimensional ornaments and vases difficult to carve directly from solid stone. Around 1970, powder-molded ornaments began to be made, and later uses included accessories, cups, ornaments, resin-mixed molded goods, and solid-stone pieces.

The polished surface of Nachiguroishi comes through a sequence of handwork. The first step is grinding the stone’s corners and whole surface with a coarse whetstone; the more carefully this stage is done, the cleaner the final finish becomes. Then #150 sandpaper is used with water until the whetstone marks disappear.

The surface is then worked through #320 and #600 wet sandpaper, each step reducing the marks left by the previous one. Waxing follows, then brushing and wiping with cloth. Whetstone, water, sandpaper, wax, brush, and cloth turn the dark rock into a surface that holds a deep black shine.

Nachiguroishi remains connected to named makers and workshops in Kumano. The working names include Okamuro Goishi, Kariya Baikando, and Tano Nachiguroishi-ten; Kariya Baikando is placed in Kumano-shi Kamikawa-cho Kounoue, tying the workshop address back to the stone’s narrow place boundary.

A 2021 successor recruitment project connected Nachiguroishi work with processing, sales, public communication, and product development. Continuity here is practical: a Kamikawa-cho material, hands that know wet sanding, Go stones and inkstones, powder-molded goods, and people prepared to keep those tasks moving in Kumano.