Keiseki, or keisekizuna, is a substrate of volcanic origin, imported from Japan.
It is a pumice stone, with physical and chemical characteristics very similar to the Italian pumice that is often used lately for bonsai substrate.
Its hardness is very high, greater than that of the akadama, which reduces the need for transplantation. It also has a high water retention capacity, and a neutral pH, around 7.
As it is a land of volcanic origin, it is recommended, for bonsai, its use mixed with akadama, which is a clay, in different proportions depending on the type of tree, its state of formation, and the climate of our area.