Tsushima Kuro Nagura Medium-High Grit Japanese Natural Sharpening Stone 4lb. 14.1oz. (2226g)
208mmx77mmx50mm
In general speaking, Kuro Nagura is medium high grit stone.
Hardness-------------8.7
It raises good enough amount of slurry for sharpening quickly.
(Scale; 1 to 10, 1-3 is very soft muddy rough grit whetstone 3-6 is soft medium grit whetstone, 6-8 is hard medium grit whetstone, 8-10 is fine grit whetstone)
Particle Size--------- 7.8
(Scale; 1 to 10, 1-3 give deep scratch marks to the steel, 3-5 is delete the 1-3 scratches, 5-8 makes the steel cloudy, 8-10 makes the steel semi-mirror finish or mirror finish)
My white I steel blade knife Jigane became frosted silver color, and Hagane became from bright silver color finish to almost semi-mirror finish.
Natural whetstone has more wide capacity than artificial whetstone, and actually, we do not know until sharpen blade on the stone. Sometimes, treasure whetstone is found after used it for a while. Never know until then.