The Kamuikotan Stones of Hokkaido
The jet black and dark green Kamuikotan stones from Hokkaido province have been well known among Suiseki and garden stone enthusiasts since the Meiji era. They are found in various forms, some with a smooth surface while others have a rugged appearance. Some of the best have circular depressions formed by centuries of wear from fast river water flowing in tight circular patterns on the stones. Some of the better Kamuikotan stones have been featured in major exhibitions and their catalogs. Many fine examples of these stones were featured in the book Beauty and Heart of Stones (Ishi-no-bi-to-kokoro) by Yoshida Bonseki in 2014, a volume devoted solely to Kamuikotan stones.
These stones were collected along the upper half of the Ishikari River, the longest river in Hokkaido, in an area known as Kamuikotan. This name originates with the indigenous Ainu people who lived in northern Japan prior to its development. It is a combination of two words—Kamui (diety) and kotan (village) or “a village where a diety lives in the Ainu language. This area was once known as “the village of a ferocious diety” because it was a difficult area for boats to pass due to the many large strange rocks.
The geology of this area is closely related to plate tectonics events. Geologists think that 160 million years ago an oceanic plate with old basaltic deposits from ancient underwater volcanic eruptions moved northward and collided with a continental plate. A belt of metamorphic dark green serpentinite from the mantle rose with other deposits to the surface in this area. This belt was first described by a U.S. geologist, Benjamin Smith Lyman in 1874. Lyman was hired to prepare a report of the geology of this island. This region of the Ishikari River contains beautiful serpentinite, basalt, andesite, chert and jasper stones. This variety of different colored stones can be clearly seen along the bank of the Ishikari River.
The jet black to dark greenish, water-worn basalt and serpentinite stones make excellent suiseki. The related minerals chert and jasper likely account for many of the dark reddish stones found in the Kamuikotan region. Actually, any stone removed from this area can be called a Kamuikotan stone. Several different types of these stones based upon their color are identified by local stone collectors. Seven types were recorded in the book Stones of Japan (Eastern Japan) published by the All Japan Suiseki Association in 1966. The current types recognized are: pure black, dark green, snake colors (many colors), five-colored, dark blue or eggplant blue, green with white, red, and golden. The golden colored category is the newest type to be recognized.
Many of the larger black stones were removed in the Meiji era and used as garden stones. Medium-sized and smaller Kamuikotan stones were displayed in trays with sand or in carved bases. These range in size from tiny stones four to six cm wide to stone nearly a meter wide and weighing over 50 kg (110 pounds). Most members of the local stone clubs in Hokkaido prefer to collect and display stones that do not require any modifications or enhancements. When collecting, they look for stones that have suitable natural bases. Most of the stones found along the river in this area are semi-flat due to the long-term effects of fast flowing waters, sand, and gravel.
There appears to be an abundant supply of black and dark greenish stones in the upper reaches of the Kamuikotan River. This will continue to attract stone collectors and provide nice stones for future exhibitions.