Thanks everybody. I went back out last night and got a rude reminder of how easy the dacite was. First I busted into a chunk I got from Cipriano and was pleasantly surprised with what was inside...
From there on it went downhill as it was so round on one side I could not get an angle to thin it. I pretty much have a flint tennis ball now.
So I grabbed a larger cobble and had a nice preform started, hoping for a blade when...
I snapped it. I think I hit just a little too high and with raw flint like that I was really swinging. Interestingly enough, I got the thinning flake I wanted, which also broke in half. Weird. I'm sure missing that dacite now. Might go look for another piece of it.
George