Entering the Jnat rabbit hole. May God have mercy on my wallet...

[Brian Holcombe]

My dad's old co-worker has been teaching me about natural stones from Japan and he explained a stratum like suita for example has always been highly coveted in Japan by carpenters and chefs. The dwindling supply of suitas is what's left in stock at wholesalers and distributors and what appears on the second hand market. This scarcity makes suitas quite expensive, the good quality ones can range from €100 for a smaller stone to €300 or more for a larger stone. A stratum like tomae is much thicker than the suita stratum and produced an abundance of good quality stones so the stock pile of tomae stones is much larger and the price lower.

Very much true in fact the old mines (now closed) have been mined since the time period when they were needed for military purposes (katana sharpening). Many are still reasonably affordable but the stones range pretty drastictically with collector grade going to several thousand USD.

[Edwin Santos]

Interesting. I will say that the methods I've used don't offer much for feedback on the finer grits, i.e. I can't tell if it's cutting without flipping over and looking at it. I might as well be rubbing the iron on a countertop. That said, my current process (hollow grind, 3m film on glass + strop.) produces an exceptionally fine edge. I'll back slowly away from this rabbit hole.

I think I'm with you. A special stone like this is beyond my woodworking needs and probably well beyond my skill level.
Something to work towards maybe.
Interesting to learn about these stones, and I admire those that are working at a high level where they make a difference.
Makes me feel like the kind of neanderthal that drags his knuckles on the ground.

[Jessica de Boer]

A few weeks ago I received this stone as a gift from my dad. His old co-worker personally knows the owner of the Maruoyama mine which apparently is the only active mine left. My dad asked him if would be able to get me a high quality stone that will last me the rest of my career and this is what I was given. It's 163mm long and 83mm wide so even though it's not a full size stone it still has more than enough surface area. The thickness though is a whopping 60mm. This particular stone is called a shiro suita. Shiro means white and oftentimes this term is used loosely and a light grey stone like this one is also labelled as a shiro suita. I was told pure white shiro suita stones have always been very rare and this a widely accepted practice in Japan.

[Brian Holcombe]

Sweet! That has some heft to it.

[Mark Rainey]

Jessica, very nice shiro suita. What edge do you get sharpening on that stone?

[brian zawatsky]

Wow that is certainly impressive!! That’s one of those $2k stones that Rob was talking about lol

[brian zawatsky]

Here’s a shot of the result from my Tomae stone. It’s comparable to about a 10k synthetic in sharpness, but the bevel is much smoother than off of a synthetic. Also, I went directly from a 1k shapton to the Jnat and it removed all the 1k scratches while polishing. I was impressed. I would imagine that the Shiro Suita above would produce a more refined edge with a better finish.
9A63B56F-4A9D-4508-B696-9896E24E6FED.jpg E2E062D2-2247-432B-88E4-BB12AA17CFFE.jpg

[Jessica de Boer]

Jessica, very nice shiro suita. What edge do you get sharpening on that stone?

That depends on how I use the stone. When I use it with water the finish is in the 8000 grit range. When I make a slurry on it with my diamond plate the finish is in the 10.000-12.000 grit range. This stone is quite hard which is why I suspect the finish is less fine with just water. I have to use quite a bit of pressure to make it release a slurry. What I found interesting is that the slurry I make with my diamond plate makes the stone release even more slurry even with moderate pressure. It not only abrades the steel but the surface of the stone as well.

[Tom Beltran]

This is very interesting. I tried googling for Jnat stone, but I am still unclear what specific stone a Jnat is. About 40 years ago I bought a Japanese natural stone, which gives a terrific edge, much better than the black Arkansas stone I had been using. But maybe someone can identify it, because I cannot recall where I got it. Only that it was natural and recommended for a better edge (which turned out to be true). For the times, when I bought it, I felt it was expensive, being more than than the Arkansas black stone. I put a little water on the stone to bring out the color. It is 58mm x 163mm x 25mm. It hasn't worn much in all these years. One thing though was I was surprised that for the money, the stone is glued to a brown plastic base. It is easily flattened with a diamond "stone." IMG_1746.jpgIMG_1747.jpg

[brian zawatsky]

That’s a nice looking stone Tom. The term “Jnat” is just shorthand for Japanese natural stone. There is a very wide variety of stone types out there, it can be a bit confusing.

[brian zawatsky]

Here’s a link to a website that contains some good info on the different strata of rock that these stones come from.
http://www.tomonagura.com/jnats/japa...a-bambata.html

Glossary of Japanese terms as they relate to stones:
http://www.tomonagura.com/jnats/japa...-glossary.html

[Jessica de Boer]

I asked my dad's old co-worker what his all time favourite stone is and he sent me this photo. He told me it's a very old Okudo suita that was mined almost 100 years ago. It's 240x95x55mm in size. That's what I call a big stone!

[brian zawatsky]

Yeah that’s a monster for sure. And a beautiful stone to boot.

[Tom Beltran]

Thank you Brian - I had never heard that term used.

That’s a nice looking stone Tom. The term “Jnat” is just shorthand for Japanese natural stone. There is a very wide variety of stone types out there, it can be a bit confusing.

[brian zawatsky]

Question for you experienced Jnat users: do you rinse and dry your stones after use, or do you let the slurry dry on them? Why?