About This Item
Mikawa Shiro Nagura ?2lb. 10oz. (1188g) Natural Sharpening Stone
207mmx60mmx45mm I do not know which mine was from the stone in Japan, but if it is ok to guess it, I guess it is one of Mikawa Shiro nagura (atsu, botan, tenjyo, mejiro, or koma). It looks more like botan knid of grit.
Hardness--------8.7 It raises good amount of dark slurry. It is kind of hard condensed stone. It is very smooth stone.
(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 makes my blue II steel Hon kasumi blade knife Hagane became semi-mirror finish. and Jigae became very nice light frosted silver color finish.
(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)
According to Dr. Kuniichi Tawara who is a Metallurgy doctor, and very famous Japanese sword researcher, Koma molecule is 10 to 20 micron. It is used right before sharpening Uchigumori whetstone in Japanese sword sharpening to delete whetstone marks from one before process Chu Nagura (atsu) sharpening. For razor sharpening, it is used one before the process sharpening by fine grit whetstone like Nakayama, Ozuku, Wakasa, etc.