I've recently been (once again) reacquainted with the qualities of this unique stone and thought that I'd re-post an old blog article I wrote years ago to share my thoughts on how this stone works.
The Misunderstood Kitayama
If there's ever been a stone that's been misused, misread, misdiagnosed, and mislabeled then it's got to be this one - The Kitayama 8000x.
I could go into great detail about all of this but I'll spare you my thoughts and instead provide a few things I feel to be facts that will hopefully explain why this stone is so misunderstood and often, as a result, mislabeled and misused.
Besides being labeled as an 8k stone it has little more than this in common with other stones in this grit range. Typically an 8k stone will sort of pull along a 4-6k grit edge to a mirror polish very quickly while at the same time will provide an even crisper "bitier" (yeah I know it's not a real word) edge but this isn't something that the Kitayama does. If used as an "8k stone" it will fail in comparison to others as it does not appear to refine lesser edges easily.
Over the years I've had an off and on relationship with this stone. I've tried many times to stop using it simply because I wanted to reduce the number of stones I was using on each knife and I wondered if this stone was doing any good at all. One thing that's become evident to me in all this time is that it's role seems to be that of an edge finisher much more so than a typical 8k stone. I've found it's best used following great polishing stones such as a Naniwa Chosera or SuperStone 10k or the like. It seems to take what these stones do and make it better. This is why I tend to think of it as a "finishing stone". I also have some theories on it providing increased edge retention but this isn't anything that I could prove so I won't go into that here.
For the surface finish (or appearance) that this stone imparts it's often been labeled as a stone that provides a cloudy hazy appearance and to this I used to agree with, however, since I've stopped using this as a stand alone 8k and now follow other polishing stones with it, I get deep mirror luster instead. The finish it provides me often imparts a depth of color which transforms bright shiny edges to a deep darker 3D appearing sort of a look. I'll often see extremely fine wispy lines within the reflections. I'm assuming that the wispy lines come from the natural stone particles contained within the stone's matrix but I have no way to know if this is true or not.
For me the Kitayamais a stone that I just can't seem to live without.