The term "Abo" as defined among flintknappers is used specifically to mean "no copper"- it means using only organic percussors and flakers like wood, antler, bone, or hammerstones. Copper was used some in ancient times, even in NA-but not much. First, it only outcrops in pure form in a few places, second, you don't need it to knap, you can't do anything with copper that you can't do with stone, antler or wood; and third-copper was waaayyy too valuable to most NA cultures to use for tools. There's been a lot of copper found in Mississippian mounds around here, but very little of it was made into anything but ornaments and jewelry. A modern analogy would be making a knapping billet out of 24 carat gold. I bet it would work great, but it ain't gonna happen.