Looks like some kick @$$ chert to me, but I'm no geologist. You are right about quality of chert and heat treating, some can be heated and made better and some can be heated and made unusable. Depends on the rock. I think a rule of thumb might be, if the rock is grainy it will work better if treated, if the rock is already smooth and glassy/waxy, it should need no heating. Most guys spall them out and get close to a preform/biface before heating. Larger rocks take longer to treat. There are several old posts that discuss heating. What's your next step? get you a big rock and find the convex side of one of those chunks and smack it w/ a downward/glancing blow and see what happens. Old broom stick w/ a 2 1/4" piece of grounding copper stuck an inch into the end will work for a pressure flaker, a rock, a solid piece of aluminum or copper rounded on the end will work for a purcussion flaker to start with. Get yourself started and the tools will present themselves as you look around for something else that might work. antler is the "old" favorite, but modern materials seem to make the work less frustrating when just getting started, IMO. It's gonna be frustrating reguardless unless your a natural. You came to the right place for answers, but be Careful, it's addicting. dpgratz