A scarce suita from Kitsuyama mine area near Narutaki, this is a dense highly compacted stone. The Narutaki area was known for their large tatami size stones. This example was shaped from section of one of those. A razor of fine craft size, it can be used as a hand held stone. Being a Mohs 3+ hardness its mass is noticable the moment you pick up up this 1.95 pound stone.
 
I found this stone to be especially affective honing heavy vintage  razors like Joseph Elliot and Wade & Butcher. It will of course hone other steels in knives or tools but you will have to test it. I shave tested those blades and the shave was superb.