Help with Breaking Jasper for Tumble

I don't think these are too sharp for tumble, but if the coin is a quarter, this batch seems to be too big for a 5lb barrel. Maybe only put a couple of the biggest pieces in and a bunch of the mid to small pieces, and you should add quite some small fillers. Plastic pellets might be consumed too fast in stage 1.

IMHO, there's nothing that's too sharp, especially for the coarse grind, as any of the sharpness should end up being ground away and/or rounded more. Some folks are perfectly fine using a hammer, but you have touched on the possible waste issue. A chisel may be more focused...have you tried that?

If you don't mind flat surfaces in your rough, you can always get a tile saw to size your material down. That's what I used. If your rough is larger than what the blade will cut in one pass, you can roll the rock so the rock is cut all the way around.

And, as far as plastic pellets go, don't use them for the first stage. Doing so kind of defeats the purpose of what you're trying to accomplish with the coarse grind. You want the rocks to contact each other as much as possible, and "cushioning" will only slow the process down.

ETA:  That's nice looking material.  If you don't mind, where did it come from?

Here are a few pieces I collected in the last month.

I've never been there, so I had to look it up. I think I was confusing it with Clear Creek, but I can't even say for sure.

Considering Stoney Creek is supposedly 75 miles long, you obviously found the right spot. Well done...the material is beautiful.

This piece is a fantastic example as to why I fell in love with Stoney Creek material!

Save the larger pieces for when you start slabbing and cabbing. However, you could break them into smaller pieces, just be careful. Is Stoney Creek the same as stone canyon jasper? It is some mighty fine brecciated jasper.

That's it!  That's the location I was confusing things with. I knew it to be somewhere near Parkfield or Paso Robles.  Thanks for clarifying and mentioning it.  Now I feel better.

If my Google search for "pedestal bench grinder" turned out results like what you have, my initial inclination is "no."  The main reason for me is I would want to work with an appliance that has the ability to grind things while wet, simply to keep the dust down, even if dry grinding with a mask respirator.  Sure, you could grind it while dry, but you'd be throwing silica dust all over the place, and you'd have to clean it up at some point in time.  I'm guessing that even before cleaning the dust, you'd be walking through it or cleaning up without respiratory protection, and it might even be on your clothes...thus a still potential hazard.  That may be extra precautious, but that's just me.

Depending on how much grinding you're expecting to do, an inexpensive tile saw *could* be an option.  The blade will turn through the water in the sump, and you can grind against the side of a sintered blade.  I did my minute grinding this way, and it worked pretty well.  At the same time, you can use the saw to help size down some of your material.

There are probably other ideas I'm not aware of...maybe even related to using some type of lap or a cabbing wheel, but that's beyond my scope.  I'll be paying attention to see what others have to add.

Some individuals.