I've been using my Dremel tool to etch flat river rocks. It does a pretty good job, and makes some nice souvenirs for our visitors.
Problem is, I haven't found a bit that'll stand up to any amount of engraving.
I tried a "diamond-chip" bit that went smooth in just a few minutes.
Right now, I'm using a small stone grinder bit. It's holding up OK, but the lines are coarse.
Any suggestions on what I might use on this pretty tough rock... ??