What material was used depends on your geographical area. In the Northwest it was predominently obsidian. In the midwest and east it was one of many different varietys of chert.
I knap and have mason jars of points, heads, and various sharp things I have made. Knapping is about 60% science and 60% art. Yea that is what I meant to write. Only someone who knaps can totally understand it. I have a pretty good grasp on the science and about 2/3 of what I start turns out close to what I intended. The other third either breaks and gets turned into somthing else which often breaks or I change my mind half way through and do somthng else and break about a third of thoes. The art I don't have down yet. Look at somthing made by D.C. Waldorf, or any big name, or countless others who are not known and the art becomes evident. I am still amazed by some of the things I see some of these guys make. I make a couple small knives a year, mostly for blanket prizes at rondys, if I find a nead arrow head I will try to duplicate it, and so on. Most could do a far better job than me.
But to the original question, yes, I have knapped glass. Glass is onery to knap, just a little bit more so than obsidian. Platform prep becomes more critical, and you crush more edges. I end up doing more preasure flaking and end up bleeding more. Hoever some of my nicest points are bottoms of old brown gallon jugs I dug out of old dumps and thick window glass.
