I'd like to learn more about the coticules and mystery hone I bought

[str8six]

So I bought a collection of barber supplies because it contained a couple of vintage natural combo coticules. They're about 5" long by a bit less than 2.5" wide and are quite thick (quarter for scale, paper for white balance). I wonder if anyone can tell me more about them, what vein they might be from, etc.

This one has these little red lines that seem to be some sort of mineral?

Whereas this one seems like it might be a bit cracked or something and someone used something black to seal it? On the closeup it looks obvious but I cannot catch my fingernail on this for trying, the cracks are imperceptible to touch. So perhaps these cracks don't diminish the utility of the stone as a hone?

And then there is this super tiny hone like thing. It doesn't feel quite as fine as the coticules though not as coarse as it looks. But if it's not a finishing hone... why is it so very small? Maybe it's something to touch up scissors?

 

[stone and strop]

Those are very nice looking Coti's !
Deep Rock and Old Rock Coti's are usually that size. It is a barbers special for sure. I would bet they are great stones. The dark line is a manganese line. Don't need to do anything with it. They are common and not an issue for honing.
Nice purchase.

 

[kelbro]

The very small one is most likely an arkansas.

 

[str8six]

Thanks, that's useful, now I have some keywords to look into: "deep rock" and "old rock". I wonder if they're comparatively rare?

And ya, when I first saw the picture I thought the small one might be an ark but now that I have it ...it feels markedly coarser than the coticule and you can see it's fairly grainy in the closeup. Having never handled an Arkansas stone though, I wouldn't know. Novaculite is apparently very hard and I suppose this would need to be in order to be made so thin without breaking so that makes sense. Must have taken a long time to wear the gouges in the sides of it.

 

[psfred]

Last stone is an Ark of some sort. The "gouges" in the sides are from sharpening knives with heavy bolsters after the edge is worn above them -- they need to be ground off at that point, but no one ever does.

Lap the Ark on silicon carbide paper on something flat before using it, soft arkansas stones are often badly abused with excessive pressure to make up for being burnished. I have one that is still too dished to use on one side, along with being glazed with swarf. You won't be able to hone a razor on it until it's flat unless you want a severely convexed edge.

 

[David]

The small stone looks synthetic from here, but I’m looking on my phone.

Both cotis look great! Nice grab

 

[psfred]

From here it looks like a small Ark for sharpening knives, we have a couple knocking around here from my Grandpa. Don't need a huge stone to sharpen pocket knives.