Well, I don't know but I've got a bunch that look like that in my chip pile that I've made over the years. It looks like a biface that failed fairly early in production. When they snap at that thickness it is almost always due to a crack, seam, bedding plane, or whatever you want to call it that creates a weakness in the rock. Lots of that kind of nonsense in quartzite. If so, though, almost certainly would be found near the rock source and should be associated with other debitage. If not, maybe a flake core?