Shobu Iromono Japanese Natural Sharpening Stone 1423.6g (3Lb.2.2oz. )
The company used to mine Shobu (it was one of them, I think that Shobu had been mined by more than one company. There were more than one ore port owned by more than one company) and the other name mines.
Shoubu-dani is the original mine to yield high quality Japanese sword sharpening whetstone in Kyoto, and the mine run out the production of the ore, and moved to the other mines, so Shobu-dani used to have really great final finish whetstones.
Hardness--------- 8.4 (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) It produces very good amount of black slurry quickly, so it might not need Tomo Nagura or a device that produces slurry.
Particle Size-------------- 8.2
(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)
It makes my blue II steel blade knife Jigane to bright frosted silver color and Hagane became bright silver color with very fine whetstone marks to semi-mirror finish. Shobu is located on close by infamous mines such as Okudo, Ozuku , Nakayama, and Narutaki, where is the east side of Atago mountain. It is original mine of Awasedo in Kyoto since 800 years ago.
Natural whetstone has wider capacity wider variety than artificial whetstone, and actually, we do not know until sharpen blade on the hone for a while. Because artificial whetstone molecules do not break down to smaller sizes, but Natural whetstone molecules are possible to break down to smaller sizes, and those molecules are mixed with sharpened steel molecules, and make Jigane as suitable Jigane color, and Hagane as suitable Hagane color.