Pennsylvanian Whetstones

[musicman980]

Top stuff C! Those are some amazing finishes .

What is it that makes you think they're slates btw? Given your descriptions of them and the pics, they don't seem like slates to me. I'd be reasonably confident they're shales - because of the sedimentary appearance to the surface combined with fissility in the structure.


(Or an outside chance on some kind of slightly siliceous carbonate - you could test this with acid.)

I was wondering when you'd show up! Thanks bro

I only say they're slates because they are found among bonafide PA black/grey slate, but that's all I'm really going off of there. I'll PM you about the acid test and stuff.

 

[Heckel7302]

Speaking of Pennsylvan-iangan, these do need a name. I’m not into names like “black shadow” or “stone of a thousand truths”, maybe something a little more direct.

I would try emailing some geology professors in PA with pics to see what they say. They might be fascinated with this and be able to narrow down exactly what they are for you. This department seems promising

https://www.geology.pitt.edu/people/faculty

 

[musicman980]

I have been searching for a suitable backing material for the brown PA polishing stones for the past several weeks now and have come across a black slate or shale that could fit the bill. It is a mid grit stone with a very consistent scratch pattern which I find completely appropriate for day to day edges and finish. On average it can come in thicker pieces which is great for adding mass to a combination stone. It is stronger than the brown stone, but not very strong, which is the only drawback I can think of for using this as a backing.

Seeing that these black pieces are useful in their own right, I may decide to glue them to their own harder backing. Gluing a brown polishing piece to one of these is not out of the realm of possibilities though, like a combo coticule.

The finish is consistent, usually either 1-2k or 3-4k depending on the piece. In some angles you can see the scratch pattern and in other angles you can only see the contrast. The edges feel refined with a little bite - great for the kitchen. Much like the brown PA stones they don’t release much mud on their own under a blade, but will readily release mud under a diamond plate or matching slurry stone. They work best with a slurry, which is inky black in color.

 

[deltaplex]

Can't wait!!

 

[musicman980]

The brown polishing stones are as rare as hens teeth, and out of the ones I do find a fraction of them are suitable for the job. While searching for them I did find these beautiful examples. They are a greenish grey color and often have a brownish cloudiness. What’s most important though is the polish, and I find it’s really close to the brown stone polish. I would still say they give better contrast than any jnat I have seen.

They feel a little sticky under the blade, especially on water. Build up a mud and the effects happen quick. Not thirsty, really fine, sort of hard but not glassy and very friable under a diamond plate, and they all give an amazing polish.

 

[birdsfan]

Wow! That is an amazing contrast!

 

[BillHanna]

Have you learned anything more about these stones?

 

[musicman980]

Have you learned anything more about these stones?

I have learned a few things in the past few months. Some of the earliest pieces that I found which were black and grey have turned out to be phenomenal razor stones. The mica sparkle in the example below is crazy, and it feels so buttery under the edge, which is surprising because it's a really hard stone. I've been honing and touching up my razors with it recently and I can't really ask for anything more from a razor finisher. I'm trying to switch to more locally sourced goods and services, so there's a chance this PA razor stone could take precedence over my jnats.

The polishers also make excellent fingerstones. I do think that because they are rarely found in larger sizes and their strongest polishing attributes are contrast and streak-free finishes, the PA polishing stones may be destined to be fingerstone material. I'll make a new post here about that.

Another thing that unfortunately could only be learned with time is that these stones can crack if you don't seal them, like most other natural stones. They are found out in the elements which may contribute to their propensity to split.

 

[BillHanna]

It seems the stones should be named after you. Get your name in the history books!

 

[musicman980]

Here’s a sneak preview of one of the coarser PA fingerstone finishes. It only took a minute or two and the fingerstone was about 5mm thick.

 

[lukoma666]

I have learned a few things in the past few months. Some of the earliest pieces that I found which were black and grey have turned out to be phenomenal razor stones. The mica sparkle in the example below is crazy, and it feels so buttery under the edge, which is surprising because it's a really hard stone. I've been honing and touching up my razors with it recently and I can't really ask for anything more from a razor finisher. I'm trying to switch to more locally sourced goods and services, so there's a chance this PA razor stone could take precedence over my jnats.

View attachment 205556
View attachment 205557

The polishers also make excellent fingerstones. I do think that because they are rarely found in larger sizes and their strongest polishing attributes are contrast and streak-free finishes, the PA polishing stones may be destined to be fingerstone material. I'll make a new post here about that.

Another thing that unfortunately could only be learned with time is that these stones can crack if you don't seal them, like most other natural stones. They are found out in the elements which may contribute to their propensity to split.

that is a gorgeous rectangle

 

[Vasco Veríssimo]

I spent a while doing the same thing with Portuguese shale and slate.

I found some stones that worked, but never anything like this. This is on another level!

Japanese stones have their reputation for good reason. But there must be many places around the world that just have phenomenal stones to polish and sharpen steel.

 

[BillHanna]

Bumping this thread, because I live here and want to make sure everyone reads this.

 

[musicman980]

Here's a little snack for you stone sharks out there. This was a find from last year - it's a harder shale, but the particles are very similar to the original brown stones.

 

[Blank Blades.]

They bring out a lot of contrast on AS too. The core looks a little grainy up close, which I guess is the grain of the steel? When I first saw that effect I reset the finish on a fine Nakayama with and without slurry, then redid the PA finish and got similar results.

These seem to perform a lot like uchigumori but with exaggerated effects. Like uchigumori, I think what’s happening here is that the particles themselves are generally coarse but also soft so they resist scratching hard steel. They make the jigane super frosty and more or less buff the hagane.

View attachment 176902View attachment 176903View attachment 176904View attachment 176905View attachment 176906

Likely hard carbides formed with the tungsten, and maybe some of the vanadium (idk how much if so) likely in bands. That are not being abraded by the relatively soft silica, thus allowing it to show up when polished.