Vintage Nakayama Maruka Karasu Japanese Natural Sharpening Stone
749g (1lb. 10.4oz.) comes with an old paper box.
Size: 190mmX70mmX23mm
The sharpening surface has black color Karasu pattern, and one of the long face side shows Karasu black layers.
***Some of the pictures were taken dry condition, and, and some of them are taken wet condition in the pictures, hopefully, it shows better the stone itself***
Maruka stamp on the side vividly.
The stone is very nice shape.
It is Khaki color stone with black Karasu pattern and light brown color spots.
#6000 to #10000 or higher grit for finishing razor blade or high carbon steel blade.
Hardness--------- 8.7
It raises very good amount of black slurry quickly, and it is kind of hard and condensed stone.
It is very smooth stone.
It looks no problem for sharpening on the black color sharpening surface portions.
It does not need Tomo Nagura or a device that raises slurry like Diamond lapping 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)
Particle Size-------------- 9.0
(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 became from bright silver color finish to semi-mirror finish, and Hagane became clean mirror finish, no cloudy looking, clear mirror finish.
If I am a collector, definitely, I will keep it.
Nakayama whetstone is finest whetstone that had beeb mined in Kyoto for almost 900 years ago. I think the mine had been closed more than 30 years ago. It had been very important as military affairs, because it is sharpener for weapons, so the mine had been protected by the Emperor of Japan or Shogun or Japanese Government for a long time. Only Honma family could have mined for a long time. Nakayama Maruka is highly sought finishing whetstone even in Japan, because the mine was closed, and harder and harder to find. It is ideal razor hone or the cutlery that needs very fine finish.
Probably #6000 to #10000 or higher grit with the same as artificial whetstone.
Natural whetstone has wider capacity than artificial whetstone has, 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 unbond 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. It is natural mystics.