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I used to use a diamond cup wheel all the time when I was doing more stone work. My strategy was to lightly nip the stone on a 4" x 10" diamond plate to ID the high points, then grind on those a bit...

Absolutely. I can tell that he has never tried to lap a hard stone, lol. Trying to lap something like the piece of jasper above on a belt sander would be like an exercise in futility. You might make...

For sure! I use mine all the time.

Being exposed to the weather, with any loose sedimentary layers the stone will only tend toward falling apart. You'll want to look for tight, thick pieces and coloration can be an indicator but only...

Lol, you and me both!

The thing for me is that the "automated" plates like that don't get the random motions down to spread wear evenly over the plate surface - I have been lapping with mine for about 6 months and dozens...

Here's my plate, it's about 7" x 13" and double-sided:

http://i240.photobucket.com/albums/ff6/eKretz/Pub/IMG_20140918_122141.jpg~original

AR should work the best out of the steels, it's pretty tough stuff. I have machined AR400 quite a few times, it's a PITA.

I use a grooved cast iron toolmaker's lapping plate.

Gotcha - here's an easy way to make it work without the guide: take a can of cheap spray paint or something and coat the stone really lightly, then use your lapping plate to give it a few scrubs. Hit...

Shaun get an angle grinder and a diamond cup wheel. Get closer with that then go to the lapping plate - or, as I prefer, loose SiC grit. That 1-2 punch makes pretty short work of even the hardest...

Yep, most use water for everything though - quartzite and novaculite will glaze a metal bond diamond wheel over in seconds if water is used though. They can be unglazed by using a"dressing stick " on...

All quartzites are very hard. They are even hard on the diamond abrasives - just like Arkies. If you're using a diamond cut off wheel at all you should use oil lubricant to cut them - otherwise the...

I check on a small lapped area. If you check just on the rough stone you can get some idea if it will cut steel but it won't give you a very good indication of cutting speed or finish. Over time...

I usually look for sedimentary rocks or rocks that fracture conchoidally then do some quick preliminary tests with a piece of old file to see if it cuts hard steel, also use the hammer test like...

That is an interesting looking stone. From the picture it looks to be coarsely textured, but I think this is not so if it will refine an 8k edge.

I have sent a couple of the stones I found out for...

Yes it most surely is, but without a burette you won't be making accurate measurements that way either. When a stone is regular (square and parallel) and able to be measured to a reasonably fine...

Yeah, mine is also regular, I just measured all the dimensions to .001" with a digital caliper and calculated volume, if anything the volume will be a little bit less than calculated, with the stone...

Did you guys measure your S.G.? I measured mine as accurately as I could but only have a postal scale, so not sure how accurate it is - measured out at 2.67.

Check the Ark thread!

It won't shine all the way through, it only penetrates about 1/4". A regular black Ark will block all light.

That's not an edge reflection. The light source is inside the edge. For it to be a reflection the light would have to be outside, past the edge of the stone. It is translucent, the same as mine is.
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That one's unique! Mine has a few of those black spots and a black streak on one side, and a spot/patch of brown on the other.

Yep, mine is exactly like that - mine is 1" x 3" x10" and the light goes through pretty much exactly like yours.

:shrug: You can BUY one from Natural Whetstone. And I know there are pics of at least one in the Ark thread. Dude. Also:
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