I haven't hit a rock in many months, but I run all the spiders out of my knapping bucket, tried to remember which end of the billet to swing, and did a little knapping over at Pat's this weekend. Got one that didn't break out of some nasty rhyolite. Pretty rough, but it's sharp and not too bad for the piece of rock it came from. It's an oversized Hardaway, about 4" x2" or so.