For stone bits small enough for inlaying, you only need 4 items.
Step 1: Tools
Simple enough items. Hammer, 1.5" & .75" metal pipe cape, and a 1" wide pipe.
Step 2: Crushing
First, put the .75" pipe cap on the 1" pipe.
Second, put the stone that needs to be crushed into the 1.5" pipe cap.
Third, put the end of the smaller pipe cap on top of the stone and give the end of the pipe 1 good smack with your hammer. Watch out for your fingers if you miss!
Forth, shake the crushed stone a little in the larger cap so the bigger chinks of stone go into the middle of the pile. Give the stones another hit with the pipe and hammer like before, and continue this until the larger pieces are as small as you need them to be.
Step 3: Storage
After you've reached your desired stone inlay size, make sure to store the stones in a solid container and not a plastic bag. The edges of the stone will cut through the bag and leave a hole over time.
Hope this instructable helps you with my Bentwood Rings with Stone Inlay project!
Step 4: Experiment
Play around with stone sizes when you inlay. You might find you like a more powdery grit or larger chunks of the stone. Or maybe you like the individual pieces look over the solid color look. Maybe its the opposite for you. Try it out!