Background [This is just copied from a message @ethompson sent me]
The original mine suffered a terrible accident in the 30s resulting in production being stopped. Shortly after WWII another vein of similar stone was located closer to the surface but was quickly exhausted. The old guard in Japan will swear up and down that the old stones were superior to the ones mined in the 40s / 50s, but no one can tell me why and having sharpened on both I couldn’t tell a difference… Like most of the big name mid-grits - Aizu, Natsuya, etc. there are actually decent sized stockpiles of these in Japan, but they’re just sitting in smaller warehouses forgotten more or less.
What is it?
Well, it's probably a kind of sandstone with other bits in it. The SG of mine is 2.50. Looks kinda like Binsui, but is a winsome, light duck-egg-blue-grey colour. It's the only jnat I've ever seen that has some pyrite in it, which seems to be only tiny dots, always within the black flecks. It's very hard, yet quite porous. The surface burnishes easily. A lot of the ways in which it acts are slightly surprising given how it feels...
Sharpening
I would describe the stone as quite slow. But bear in mind that all Japanese mid grits are quite slow, as are hard sandstones regardless of where they're from. And slowness isn't necessarily a criticism; certain types of jnat can pull off an uncanny trick in which they actually produce extremely good edges, whilst appearing to do nothing at all, and I think the Tajima is a prime example. It's maybe not as easy to use as some, and tbh I don't find it immediately loveable as a sharpening stone, but with a little understanding you can coax some pretty decent results out of it. And the fact that it's almost impossible to raise a burr will also make it a very good deburring or touch-up stone.
The finish level I'd put around 3k or 4k, which is a fair bit higher than the grain or particle size that I'd guess at around 1k or 2k. A direct result of the stone being so hard.
On slurry the stone is quicker, as you would expect, but the dulling effect outweighs that. There's probably a happy medium to be found in terms of starting on slurry and finishing clean, but the edges are definitely better off a clean stone.
Polishing
Now this would've thrown me completely if ET hadn't told me already about it, because traditionally one would want to polish with stones that are soft and fine, but the Tajima is hard and coarse - basically the antithesis of something like a Maruoyama Shiro Suita. And yet it is a really excellent polishing stone, and surprisingly easy to use. One of the first things I put on it was a Mazaki, famously difficult to make look even semi-respectable, but the Tajima did as good a job as I've ever managed.
Once again it's the hardness that brings quite a considerable amount of detail and shine, but it still somehow maintains contrast on san/ni mai cladding. There is some visible scratch pattern, but it's much less prominent than you would expect. The finish level of the polish is above even the edge finish level, which is kinda ideal really. It doesn't surprise me a jot that when when he sent out the recent RDG x ATT kiridashi, it was with a Tajima polish.
And in conclusion
Not everyone will love this stone, it's too unusual for that - atypical in any number of ways. It's not the very best sharpening stone in the world imo. Not bad, just not my favourite, but who buys a jnat for edge whetting anyway? As a mid-to-upper-mid-grit polishing stone I think it's first rate.
And when you throw in the fact that these stones aren't that expensive in the grand scheme of things, and the wear rate will be through the floor - I think you're looking at exceptional value for a natural stone. I'd certainly recommend checking in with Atelier to see if there are any going, I don't know for sure but I suspect ET might have a few more up his sleeve available soon.
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. But I'd say this stone is an absolute belter personally.
