Unique Natural Stones

[ex1580]

I just got a box in the mail yesterday from France and one of the things in it was a Belgian Violet stone. Obviously it will take some time for me to form an opinion on this stone but the "range" is supposed to be 3-6k depending on how thick your slurry is which is a good finishing range for a variety of kitchen knives (and no burr to worry about hopefully!). I think it's just a pretty Belgian Blue honestly, but I am excited to use this one more. I have used it exactly once, on a razor, and I think it has potential.

[Jeff B]

When sharpening, once you reach an apex a burr starts to form. I don't see how that doesn't happen just because of the stone you are using, it's not logical.

[taz575]

With the slurry on the natural stones, the slurry itself helps remove the burr when sharpening or greatly reduces it.

[ex1580]

When sharpening, once you reach an apex a burr starts to form. I don't see how that doesn't happen just because of the stone you are using, it's not logical.

It's garnets! It is strange, but I read it on the internet so it must be true. Specifically, on the Science of Sharp site, this is why he likes Coticule stones. Cant find a link at the moment.

EDIT: Just FYI, I think it's weird too. Now that I have this Belgian stone I am going to give it a try one of these days. I'll reply back here if there are any remarkable results.

[XexoX]

With the slurry on the natural stones, the slurry itself helps remove the burr when sharpening or greatly reduces it.

Completely unrelated, but you made me think of this.

[ex1580]

When sharpening, once you reach an apex a burr starts to form. I don't see how that doesn't happen just because of the stone you are using, it's not logical.

I've sharpened a few things now with my new Belgian Violet stone and it is pretty interesting to say the least.

In regard to razors, I probably wont use it for razors again (someday when I get a coticule I may change my mind on this). My Shapton Glass 2k, 8k progression leaves a really nice edge and not much work for the finishing stone so I can do a "choose your own adventure" with what finishing stone I pick. The Belgian Violet edge is too big of a jump to the finishing stones I have, I don't care what Science of Sharp says, haha. I would be finishing the razor forever and make mistakes and not good.

As far as kitchen knives, this is where things got interesting. I sharpen my vegetable cleaver (CCK 1303) on everything just to see what happens. In this case I started the Belgian Violet with about as thick of a slurry as I could muster and only gave it a few strops on a clean stone at the end. Under a microscope it looked just like I had used an Arashiyama 1k when I was done. I couldn't tell the difference, which is fine because I like that edge and think it's just about perfect for that knife. BUT, like I said it got interesting because then I did a Wusthof knife which has been pretty burr happy in the past and while this stone didn't completely eliminate the burr (as folklore suggests) there was almost none, which is pretty nice. Not to mention that I took more time to dilute the slurry and under the microscope it looks like a 5k or so finish which might be a little too much for this knife, time will tell.

If this were work I would stick with synthetics because they get it done, but for fun a stone out of the ground is pretty fascinating for some reason.

[Jeff B]

...I did a Wusthof knife which has been pretty burr happy in the past and while this stone didn't completely eliminate the burr (as folklore suggests) there was almost none, which is pretty nice. Not to mention that I took more time to dilute the slurry and under the microscope it looks like a 5k or so ...

Did you check for a burr while you were working the edge? Maybe a burr formed but you worked it long enough to remove a lot of it. This is just my curiosity asking questions.

[ex1580]

That is a possibility. I thought I felt a burr as I was working it but I didn't check with the microscope until I was done on the stone. Next time.

[ex1580]

Did you check for a burr while you were working the edge? Maybe a burr formed but you worked it long enough to remove a lot of it. This is just my curiosity asking questions.

In the name of science I did another one. The knife I sharpened has a history of being very burr happy. With a Shapton stone for example I would need to work at it both on the stones and a strop to get the burr cleaned up. I often microbevel the edge just to save time. It is a stainless knife and we (everyone else in the house mostly) use it for basically anything on the cutting board.

Methods
This time I put permanent marker on the bevel of the knife then made a thick slurry on the stone. I then sharpened the edge in the slurry (edge leading), diluted the slurry and refined the edge with a handful more strokes on each side (still edge leading), cleaned the stone off and stropped it on the stone (edge trailing) with the intent of trying to make a burr, then alternated the strops just to see.

Results
I used the microscope a lot along the way and saw virtually no burr at any point compared to what I see with a synthetic stone (which can create a huge burr easily). When I was purposefully stropping it too much there were some tiny bits of burr visible at 120x but when I switched to alternating strops they went away. This was a significant improvement for sure. The edge turned out about like a carefully done 2k Shapton or maybe a little finer. Neat!

Conclusions
This particular Belgian Violet stone prevented a large burr from forming while sharpening this knife. More data will need to be collected before further conclusions can be made.

One thing is for sure, next time I have a knife with a tricky burr I will pull this stone out and see what happens. Here is a picture of it. It looks very violet colored when it's wet.

[trancher]

Here's another interesting stone from Indonesia. (Reach back into your mind for those geography lessons )

Made from volcanic tuff, these are listed as Red/Medium 1K, Black/Medium-Fine 2-3K, White/Fine 3-4K. What is "tuff", besides that last restaurant steak you ate? Well, "Tuff is an igneous rock that forms from the products of an explosive volcanic eruption. In these eruptions, the volcano blasts rock, ash, magma and other materials from its vent. This ejecta travels through the air and falls back to Earth in the area surrounding the volcano. If the ejected material is compacted and cemented into a rock, that rock will be called "tuff."
More splainin'

The price on these is fairly reasonable for mediums 200x50x30mm ($34)+S/H
Indonesian Natural Stone

[ex1580]

Neat! I wonder how Tuff would compare to something like a Tsushima stone which is a volcanic stone mined underwater off the island of Tsushima. It's usually in the 2-4k range and often used as a Nagura. I have a Tsushima Nagura and I really like it, although I hear they can vary quite a lot.

[trancher]

Neat! I wonder how Tuff would compare to something like a Tsushima stone which is a volcanic stone mined underwater off the island of Tsushima. It's usually in the 2-4k range and often used as a Nagura. I have a Tsushima Nagura and I really like it, although I hear they can vary quite a lot.

Good question. Google to the rescue.

"Like all Japanese natural stones, Tsushima Black Nagura are mined from sedimentary deposits created by airborne volcanic ash being sifted by distance and wind and filtered by waves and tides by the time they reach the ocean floor. But they have not been subjected to the metamorphic weight and heat that makes harder stones, and are relatively soft and permeable. They also tend to crack in the same plane they were laid down in, especially if subjected to wet/dry and/ or freeze/ thaw cycles, so special measures are necessary to protect them. "

Tsushima Black Nagura

So it looks like a main difference is the hardness of the stone. But there has to be some other factors to, just by the completely different creation methods.

[ex1580]

I think this forum needs a geologist with a sharpening hobby.

[trancher]

I think this forum needs a geologist with a sharpening hobby.

Agreed!!!

[potlicker]

I think naturals have their place in a residential kitchen and I have several Dan's and some from the Natural Whetstone Co. I prefer the Washita fine (2000 grit) from Natural Whetstone for finishing with WD40 as a lubricant. I have numerous Shapton Pros and Naniwa stones but use the Washita for a finish. Just finished up a Kanehide Petty on a 1000 Diamond Plate (Trend) and finished on the Washita......almost too sharp for a kitchen.

[Kekoa]

almost too sharp for a kitchen.

Wait, is that a thing?

[potlicker]

Gotcha!!!!!!

[weeeeeeum]

Not sure if anyone will read this but I have had some good luck with cheap naturals and some home made ones. Just like you I got bit by the natural bug but being a cheapskate and paranoid, I only got really cheap ones. Miraculously some of these were actually really good. One was a sort of J-NAT vintage koppa and is actually excellent. I've been very busy so I have not actually fully translated the text on the side but this one is legit. I have 2 other J-NATs, another bought vintage and is decent and a new Amakusa Orange.

The one bought vintage had a lot less known about it, vaguely rectangular but very out of flat. There was also no markings or documentation on what it could be either but it was cheap and it was decent sized (approx 8"x2.5x 0.75"). I'm pretty happy that I did buy it because its a decent stone. I would say its around a 2k ish finish but would probably be a lot nicer if I properly dressed the stone and practiced some. Its also pretty soft and builds a brown slurry quickly, no nagura required.

The Amakusa stone is sort of interesting and honestly I am not a massive fan of it. What is really odd is at first it was very friable and soft and a slurry could easily be started from scratch. However the more I used it the harder it got and now I need to start with a diamond plate or nagura. Once you do get a slurry it is around a 800-1400 grit finish and is meh. It gives pretty good contrast between hagane and jigane, and is decently consistent but it's quite scratchy. It seems as though the porous nature of these stones means there are a lot of coarse particulates that inevitably work into your slurry. Because of the fairly poor finish and the how slow the stone is I don't like using it very much. I am still glad to have tried it and it is excellent value (like 25$ for 1.4kg of stone!). It would make for a decent display piece because the striations, veins and colors are quite striking and pretty looking.

The cheapo chinese stone was also bought out of curiosity and similarly I do not regret this one either. It's pretty dang tough and I usually use a nagura with this one, though building slurry from scratch isn't that bad. Its a teal-blueish color and is around 4k to 6k finish. It does a really nice finish if you really take your time and build a good slurry. You need to be pretty careful because it's very sensitive to pressure. If you use a little too much you may get a deep scratch on your knife and stone. Not really sure how or why this happens but as long you are careful you don't really need to worry about it. This stone I got off of amazon for like 20$.

Now I have also tried to make a lot of my own natural stones with varying success. Much of the time they are just too hard and non friable to make for a good stone. They also often have "toxic" inclusions that will ruin a finish. They are sort of useful if you build a slurry with a nagura but at that point you are basically using a kanaban. Despite many of my natural stone projects ending up like this there are 2 resounding successes. One is a little funky nagura that works really well for working up a slurry around 1000 grit. Another is an odd shaped rock that was really soft and also makes a decent stone.

That natural stone is kind of a funny story. I was on a walk with friends and I was looking at some rocks, one asked what I was up to and I told her about my ongoing shenanigans. After that she climbed a fence and just picked up a random rock and gave it to me. I was pretty skeptical but out of respect and appreciation of her efforts I tried it anyways. Coincidentally enough it made for a really decent stone, even if very misshaped. It produces around a 2k finish though it could probably be much better if I had a stable way of mounting it. Additionally its still rough around the edges and I think that's effecting the final finish significantly. An interesting tid bit is that the stone's slurry is pure black, as if you could use it as ink which I find really interesting.

[ex1580]

That natural stone is kind of a funny story. I was on a walk with friends and I was looking at some rocks, one asked what I was up to and I told her about my ongoing shenanigans. After that she climbed a fence and just picked up a random rock and gave it to me. I was pretty skeptical but out of respect and appreciation of her efforts I tried it anyways. Coincidentally enough it made for a really decent stone, even if very misshaped. It produces around a 2k finish though it could probably be much better if I had a stable way of mounting it. Additionally its still rough around the edges and I think that's effecting the final finish significantly. An interesting tid bit is that the stone's slurry is pure black, as if you could use it as ink which I find really interesting.

I like to think this pretty much summarizes natural stones in general. Human wants to make thing sharp, looks for something to sharpen it on. Kills beast and eats it in cave.

Thanks for sharing your adventure!