Large dedicated colorful iromono bench stone for knives & tools.
This stone, 140 x 90 x 38mm thick and 1,310 grams (2.9 lbs) is from the Ozaki mine. The hardness is in the Mohs 3 range. This huge iromono will come with a large and tested tomonagura slurry stone, or you can raise a slurry with a diamond lapping plate (diamond nagura). I have tested all kinds of steel and this stone cuts them all.
The stone, as thick as it is, with its back flattened does not require a stone holder. And as wide as it is you actually have 4 edges to move around on, encouraging the even and equal use of all four sides.
The Ozaki mine was the last of the Umeghata properties to open. It was in the upper-valley region and not tunneling was necessary, the mine and its layers of unusually thick awasedo layers were exposed by the use of bulldozers.