Tsushima Black water stone

The legendary Tsushima Black Stone, found on the seabed of the Sea of Japan, has a medium to medium-high grit, approximately 4000 grit (JIS) The size of the stone without the blank is 150x25x6mm, the size of the blank on which the stone is glued is 161x25x3mm. Size and weight are not actual size and weight, but they should be very similar too. The hardness of the stone is quite high - 8.2 on the Mohs scale.   The Tsushima rock, when operated, quickly produces a fairly good amount of a dark gray suspension in the form of a not very thick, sticky gruel, and therefore it is often used simply as a nagura. The average size of the abrasive particles in the Tsushima stone slurry is approximately 7.6 microns, but since work is almost always done using loose grain, the Tsushima sharpening stone works much finer than the nominal grit for a given grain size. On the supply of a knife, as a rule (depending on the composition of the steel), very small short marks are formed, and the metal after processing with Tsushima stone acquires an unclear light gray color with a silvery tint. The Tsushima sharpening block can be recommended for use before finishing finishing with fine-grained hons such as Nakayama sharpening stones.