Pretty cool rock. It looks like it would work as a pendant. I would ask myself though, why would a person expend the energy to wear a hole in this mundane rock? Couldn't they find a prettier stone to wear around their neck?
It does appear to be drilled from one side. Most native pieces are biconically drilled, so drilled from both sides. Still, it looks like it was drilled, and not a natural hole. The question is whether ancient or modern. I am also wondering if it a waterworn broken piece of something bigger.