The wavy line between blue and yellow layer is somehow very typical for stones coming from the Old Rock Mine. And from the look at the surface I would bet this is also an Old Rock Layer Coticule (= La Veinette). But only my guess.....
Regards Peter
BBW variety
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Regards Peter
So Peter, Do you consider the true Old Rock to be the equal or better than La Veinnette from the Old Preu mine of perhaps 20 years ago?
Do you recall my asking you about this SRD Old Rock?
Oh thank you for that info Peter, very interesting.
I've never had a known/labelled Old Rock unfortunately, so couldn't really say how this one compares. Though from trying it out yesterday I would say this is a very high quality stone, probably one of the best two cotis I have, so you may well be right.
Funnily enough though I'm not so keen on the BBW side, which is quite a hard, slow and fine example. Can't win 'em all eh!
So Peter, Do you consider the true Old Rock to be the equal or better than La Veinnette from the Old Preu mine of perhaps 20 years ago?
Do you recall my asking you about this SRD Old Rock?
This is going to be one of my more speculative posts, because I don't have a huge amount of experience with them, and there are a lot of 'ifs' involved, but fwiw...
When I said above that my new stone was one of the best two cotis I have - the other one is a large piece of (I am reasonably sure) La Veinette, and they are somewhat different.
If we assume that the latest one is from the Old Rock mine then by comparison it is harder, and though it is reasonably quick it's not as fast.
The one I had already is an extremely fast stone and relatively soft, it self slurries with ease very quickly. It's also pretty fine; probably around the same level as the new one, and easily in razor territory. Though perhaps not as easy to use for that because it's quite soft and fast.
The LaV I already had produces utterly gorgeous knife edges because the raw speed means you can get some serious teeth still on the edge if you don't overwork it. The new, possibly-Old-Rock stone is a slightly better razor finisher I think, the shave off it yesterday was superb. Though both can be used for both things to remarkably good effect.
The BBW on the stone I already had is miles better than the new one.
[Told you it'd be speculative!]
I have one similar to this and it's a great razor stone. It's REALLY hard, dense and glassy.
After you hone up a razor on the yellow side try doing 20 laps on the bbw and see what you get. The bbw on mine is glassy like a Charnley and it's good for a quick, final polish. Ymmv.
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My best razor stones have been the real hard and appear to be those old rock stones which I believe speed was a key criteria in the old days of selection. One with similar cutting capabilities, but a bit softer would release more garnets and thus seem to cut faster. On the old rock if you make a slurry it will speed it up too. I guess you could make a slurry with an Atoma since you are not worried about shaving with the edge and more about knife cutting, but try some slurry using other coticules or coticule slurry stones on it and you maybe surprised. I am planning on trying this on the various BBW to see how it does.
I actually used to have a jug of coticule slurry that I’d pour on other stones to turbo-charge them, then dried it out to a powder block form earlier this year. I shall give it a go on the new one!
[This picture has absolutely nothing at all to do with my other side hobby as an international opiate smuggler.]
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I laughed because years ago I did the same thing. While lapping I would pour off the old slurry into an old dog bowl and let it dry. After a bunch of coticules I ended up with a chunk shaped like a dog bowl about that thick. I had it for a few years. I don't remember what happened to it. I bet it is in the shed somewhere.
My coticule that looks similar leaves a much more toothy edge on knives with a fairly light diamond plate slurry but any other type(aside from one bbw) the edge is smooth as butter. I actually shaved off mine earlier, my la lune edge was a little toothy and it almost felt like an ark coming from the coticule. I think la lune>fine coticule is something I'll explore in the future.
Definitely look it out, coti slurry is awesome on pretty any kind of stone!
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Here's a fun demonstration of how agressive a coti is in comparison to BBW, these are quick 1 min polishes are off different sides of the same stone:
If you didn't know what types of stones had been used here you would say that the scratch pattern from the first one is off a coarser stone. But that's the yellow coticule, and the scratch pattern is because of how aggressive it is.
That scratch pattern tells you everything about why a coti can leave an extremely toothy edge on a knife if you want it to, why it can set a bevel on a razor, and why you need to work slurry dilutions in the way that you do in order to finish one.
