I've got an obsidian cobble that I picked up decades ago, probably discarded by some stone-age Knapper because it has some fractures in curved lines and straight fractures that meet at near 90 degrees.
OK, that's my beginner's excuse, but what is happening is that almost all the flakes I have been able to remove are either thickish triangular in cross section or are just way to thick to even call them flakes. Rather, they are odd-shaped slabs. Some are just angular chunks.
Of course, you probably can't have a good idea what I am doing wrong without pictures?
