Honey Onyx Stone

[lightfoot]

So in my continuing attempt to explore odd stones for honing I picked up a nice piece of striped Onyx to play with. I had to cut a piece off one end where the saw work was incomplete. I wound up with a nice overall shape to try out. This specimen is very translucent across most of the stone and also had areas of opacity.
Now I’m in the flattening process. I’ll probably work one side up to 600# & the other to maybe 1200# or so just to establish a point of reference. Has anyone else dabbled with these stones here? Thanks

 

[sexy beast]

Interesting, let us know how it works out.

 

[Bowmaker]

Sounds like it should work.....

Cryptocrystalline - Wikipedia
Cryptocrystalline is a rock texture made up of such minute crystals that its crystalline nature is only vaguely revealed even microscopically[1][2] in thin section by transmitted polarized light. Among the sedimentary rocks, chert and flint are cryptocrystalline. Carbonado, a form of diamond, is also cryptocrystalline. Volcanic rocks, especially of the felsic type such as felsites and rhyolites, may have a cryptocrystalline groundmass as distinguished from pure obsidian (felsic) or tachylyte (mafic), which are natural rock glasses. Onyx is also a cryptocrystalline. Agates such as the fairburn agate are also composed of cryptocrystalline silica.

 

[lightfoot]

I did get both sides worked up to 600# and did roughly 40 strokes with some pressure on an edge that I’ve been shaving with for about a month straight. I would say I got an arguably smoother shave but I would hesitate to call it sharper than my limited efforts with the Jasper seemed to produce.
Honestly it’s been more about the fun factor of chasing stones that I don’t really understand...

 

[lightfoot]

When I get some time I’ll need to take a couple of blades down to 5k and then thoroughly clean them with soap and water. This might give a general idea as to whether or not there’s any cutting going on and not be fooled by swarf left on the blade from the last stone. I would only use that large of a jump just to see how things pan out because I suspect that if this stone does have an effective abrasive content it may likely best serve as an absolute final finisher.

 

[lightfoot]

So the first handful of shaves were done off this stone prepared at 1000# w/d and while the edge was very sharp the smoothness wasn’t quite dialed in. So I did something a little counter intuitive in that a took the surface down to 220# and used a generous amount of oil and worked more with my pressure. The smoothness was really impressive to say the least. The results were exactly what I was hoping for. So this process makes me want to reconsider my approach with Arkansas stones as well. Who would have thought that dropping the surface down and offsetting that with more oil was the right approach?

 

[2bit_collie]

I’ve been wondering about this myself. Been reading all the older threads on Jaspers and other hard stones, also watched some videos by the Wild Whetstones guy.

In particular what I took away from this is that getting good honing off of these super hard rocks seems to depend on having a sufficiently rough surface, possibly including slurry. I was a bit surprised at how much effort Gabriel was putting into raising a slurry and also that he was generating slurry multiple times per honing session. My current method (which I freely admit may be non-optimal) is to quickly lap my synthethic stones (2K, 5K, 8K) just enough to erase the pencil marks. I use that slurry until its gone and then typically just go off of plain water until I am done with that stone. On the ILR and black ark I don’t lap at all in the normal process. My ILR has not gotten any surface treatment at all since buying. The black ark gets lapped on 600 W/D every 8-12 uses or so, when the surface gets a bit glassy. I‘ve been using soapy water on the ark. My take-away on the black ark is that if the surface gets too shiny, it might not really be doing that much. But of course if that is my finisher, do I really want it to be aggressive, or am I sacrificing refinement and smoothness by having too coarse a surface?

I also have hard ark - one of the thoughts going through my mind is to perhaps experiment - what is the difference in edge results between a hard ark and a black ark both after both have been lapped on the same relatively rough grit?

Anyway, ordered a double-sided DMT plate (coarse/fine) to try out a few things in the future. The only plate I have right now is ~180, so really rough.

 

[lightfoot]

So I just did a trial experiment with a Washita prepared at 120#, a True Hard at 220#, and the Onyx set at 220# as well. I used more oil than I have in the past throughout and adding some as needed. The Onyx absolutely offered more refinement than the True Hard Arkansas stone. But the True Hard took the edge well beyond what I was able to achieve off the Washita so every stone seemed to do its job well.
Another thing that I would add is that I did 3X’s more work at every stage beyond what I was doing in past years. I do the 3X’s the work thing regardless of the stones I’m using.
I consider the following one set: (40 half strokes, 40 circles , 20 X-strokes)
I do 3 sets on each stone. Only difference on synthetic stones would be I would omit the half strokes at 8K and just move to circles and X-strokes. Also I use what I consider bevel setting pressure on 1, 3, & 5K and reducing that considerably at 8K and beyond.
But with the Washita, True Hard, & Onyx stones I probably went somewhat beyond those number of reps per stone.