Big chunk of natural black Obsidian

Responcibly resourced from my property in 29 Palms, California. Near the Joshua Tree national park. If only it could tell us its story... From the markings it looks like it may have been used as a tool, possibly on other pieces of obsidian to craft arrowheads or other tools. The reason I believe that, is becuase I found quite a few other pieces of obsidian, several of which are definitly old arrowheads. Ignore #TAGs: rock hound mineral collector geology teacher history crystal grid healing