Most good rock sources are not public knowledge. If they were, the best rock would be gone pretty quick from that spot.
![Wink ;)](http://www.primitivearcher.com/smf/Smileys/default/wink.gif)
We all ruin good rock, even experienced knappers. But that shouldn't discourage you. Try to get the best rock you can. It will save you a lot of frustration, believe me. For example, you wouldn't buy crappy arrows to practice with just because you might loose them, would you?
Glass from wine bottles is a good alternative to stone. Knap the darker colors: it's easier to see the flake scars.