#566 shiro (white) unchigumori awasedo was, judging from the from the circular saw marks, dug in the 2nd or 3rd quarter of the 20th century. And the straight namazu infilled pastel yellow inclusion indicates from the Nakayama mine, one of the Narutaki or maybe from the Shobudani mine on the western side of the same ridge. There is no kawa anywhere on this stone. Some more research will be necessary.
Softer Mohs -3, it is very easy to use. I tested several straight razors with this stone, first after raising a very mellow #400 Atoma slurry on a series of razors whose bevels were set with a #1000 King stone. Each of the blades listed below developed shave-ready edges within 40 strokes and a few after just 20 strokes and stropping on leather. 
Those honed to HHT status were:
Hart Steel
Friodur Inox
Henckels 415 carbon steel
Brian Brown
1890s Wade & Butcher
Kikiboshi 6800 Swedish Steel
 
I have also tested this stone with a group of Japamese handmade
 carbon steel knives plus some western knives like Henckels 4* Ice Hardened stainless steel knives. No problem with any of these. My method is to test odd shaped and smaller stones first with razors because razors require less surface area to hone easily. But with special small stones I also test with knives. I consider this stone to be razor size stone that will sharpen knives tothe shame sharpness.
 
This stone as well as all of my stones will come with a life-time size tomonagura that has proven to be compatible with the basestone.
 
162 x 75 x 25mm thick.
750 grams