That's what I first thought, but didn't really feel the need to express that opinion. Likely a piece of merchandise from a vendor that sells fossils, rocks and minerals.I would be sure it's neither a fulgurite, nor volcanic glass.
What it most looks like to me is a piece of smoky quartz, but surely not naturally-occurring in that form. I would suggest that someone has cut and polished it to that cabochon shape... perhaps for use as a paperweight.