Thread: Agates and Jaspers

I have seen a few mentions of agates or jaspers as finishing hones, but haven’t really seen any discussion or information regarding them. I’d like to get some opinions on their worth as a finisher and what seems to work best with them. And pictures, of course, these stones can be beautiful.


I’ll start, I have two jaspers, one is Owyhee picture jasper that I’ve used occasionally and another blue/green Owyhee I haven’t completely lapped a depression out of yet. So far my results with the picture jasper have been spotty, it improves a Cnat or Imperia edge with smooth, silky feedback on some razors, while others just slide over the surface without any feedback or improvement to the edge.
I plan on methodically testing both soon.

I have a piece of jasper that I got from a friend who is into rocks. I grid lapped it and tried honing with it and to tell you the truth I don't think I got anything off of it. Perhaps it is just my piece of rock, they are after all just a little different. I won't try that again.

Agates and Jaspers are forms of quartz. They are pretty hard compared to most honing stones. I think there are better choices.

I've used them, and I'll tell you what I got out of it (I still use them sometimes):
* you can slurry them with diamond hone, and their particles are hard and sharp, which is probably compounded by how hard the stone surface is. They will cut aggressively with a slurry on them, but I would bet not very fine.
* In my opinion, having two that I really like (i have others, just two that I lapped flat), I like to keep them clean as burnishers. That means they're sort of a post-hone aligner and you can use some pressure on them if you'd like without damaging an edge.. I do one with wd 40 and the other with water.

When you use one as a slurry stone, they do not ever release any of their own, so you'll have to refresh them if you do that. I'd expect them to be aggressive because of the hardness. I use other stones for that, but in a pinch, I'm sure I could finish a razor on one that way. I'd never lap them on a direction other than their length, though, because striations across them can damage a razor or cause ledges that create a false coarse grit (the hard edges acting like a large particle).

8:30 or so in this video, I do what I do with these. I titled the video an odd name because I suspected that with slow cutting shallow groove stones, that the direction of the cut is not so important and I'm no hone guru, but I suspect that these are close to what people refer to as half strokes.

https://www.youtube.com/watch?v=61QtXDy_Gf4

The clattery sound is the tang of the razor touching the edge of the stone.

that leads to a suggestion (beyond making sure they are absolutely flat), and that is to round the edges on them as au natural, they can have some pretty brash side edges. In this video, I intentionally kept the razor 100% on the stone, something you might not like so much to do if your razor isn't dead straight.

Make *sure* that the surfaces are dead flat lapped, if they aren't, you'll have problems. They are the hardest stones I've ever lapped, so take however long you need to do that.

re: the above with better choices, I agree if you're limited to a finisher. I will say that I could put a better edge on a razor with the jasper shown in this video (slurrying it if I had to) than any of the hone slates coming out of the UK. I know that from experience, I've had all of those types, too. The learning curve is steeper on the jasper, but they have a higher top end potential as long as you don't bring a razor to them straight off of a 1000 stone.

the black ark in my video is perfectly capable of finishing a razor (it's a dan's). the jasper normalizes the result and makes absolutely certain.

What Video?????????

Sorry about that. Fixed it. It should be clear from my view counts that I am by no means self promoting my youtube channel (as in I don't have high view videos and my youtube is not monetized - at least I hope it's not. I have an adblocker on and wouldn't see if there were ads, but it should be no ads).

FWIW, I just watched a little of that video, I was just testing an idea and not suggesting that people should scrub their razors all over stones unless they're using the same type as these. With a fast cutting stone, doing that would make a mess of the razor in terms of spine wear, etc. Also, that was a new razor that had a stropped edge but no properly set bevel, so it's not what I would do to refresh a razor. I would just put the razor on the black and jasper once every 200 shaves or so.

Marginal HHT results, too, but the whole thing shaved fine, and came around well after another cycle or two on the linen.

Thanks, DaveW, great info!

the HHT in my video shouldn't be seen as a good indicator of the potential of the jasper as a burnisher, either...I'm sure some folks will watch that and say "what's so great about it?"

What's great about it is that it makes an edge that's pretty sharp but not harsh. It's a cheap thing to experiment with, too, just be choosy about what you get and make sure it's real jasper. Travertine and some other types of stuff that look like jasper can be too soft and too coarse.

Total cost for my two owyhee slabs was somewhere around $20. They are fun to play with and do have some potential.

Originally Posted by DaveW

the HHT in my video shouldn't be seen as a good indicator of the potential of the jasper as a burnisher, either...I'm sure some folks will watch that and say "what's so great about it?"

What's great about it is that it makes an edge that's pretty sharp but not harsh. It's a cheap thing to experiment with, too, just be choosy about what you get and make sure it's real jasper. Travertine and some other types of stuff that look like jasper can be too soft and too coarse.

Total cost for my two owyhee slabs was somewhere around $20. They are fun to play with and do have some potential.

I'll keep experimenting and even if they don't do the best job, they are pretty.

I tried using mineral oil/minerals spirits 50/50 last night on my brown Owyhee. I was quite pleased with the results.