I do that most every day. Red jasper, lapis lazuli, malachite, also work well. Any opaque stone, but translucent stones like amethyst don't work...they lose their color when crushed. Best way to crush it, get a six inch piece of 2 inch galvanized pipe, put a cap on one end. Get a 12 inch piece of 1" galvanized pipe and put a cap on one end. Put the stone in the big one and beat on it with the little one. Works a treat. For larger cracks, mix the crushed stone into epoxy and poke it into the cracks. Smaller ones just use CA with the crushed stone. Brass from a key cutting machine at your local hardware store also works really well, but wear nitrile gloves to handle it...it is like handling cactus spines.