206 - 80 - 58mm
2.55 kg = 5.6 lbs.

Reads on the stone top from the upper right down in small kanji GOKUJO (extremely fine
quality).
And in larger kanji to the left HON-SUITA (the name of the strata)
The middle left edge reads BIWA after Biwa lake near Kyoto.
At the lower right corner SAIKOKYU (very best quality)

A giant 5+ pound awase toishi of superior quality and purity, stones of this quality and
character and size have not been mined for many years and come from the deepest strata of the mines of Kyoto. These mines were known to be dangerous to the diggers
because of typical mine hazards and the stone processors and the miners because of the extremely fine dust particles that caused lung disease. Most of the mines closed before 1955.

The back of the stone is very flat with some chisel marks and lots and lots of renge showing there too. None of the lines you see in the stone are structural and do not affect the sharpening qualities in any way as they are softer than the steel.

This is a very, very fine grit stone that produces a bright chrome like finish to the hagane
that you can see in the photos while leaving the jigane soft and reflective. I used a diamond plate in the central lower area to test the stone and break through the oxidized skin that has formed over the last 50-60 years. I found the stone to be very easy to use
after the diamond. Before using the plate I could sharpen and build a paste but it took
longer to do so

This Shiro (white) Hon-Suita stone came from a store in a small town in Japan that closed in the 1970s containing stock dating back to the 1930s. This awasedo has not been used other then to test the quality at one edge of the stone as you can see in the photos, and it
is considered to be NEW/OLD STOCK.

The stone as it sits looks a bit tinted buff because of the decades old microns thin skin that is the result of exposure to the air. This will come off with the first sharpening or use of a diamond plate giving the stone a much lighter tone and looking more like the white of the back. The renge is thick and purple and runs all around the stone and you can see it on the sides of the stone too. This awase toishi when top dressed using a diamond plate produces a very white paste. Using this paste to sharpen a blade produces a thick black slurry very quickly. I am recommending that all of these deep strata hard stones be top
dressed with a diamond plate and I feel that the use of a diamond flattening plate is the key to using these hard stones. I use an medium grit Atoma myself. When I do develop a paste I try to leave it on the stone after using and not wash it off to save it for the next time I use the stone.

This stone has tremendous cutting speed/strength and produces black water within a few
strokes.