A couple of years ago, we were hiking at the "Big Obsidian Flow", at Newberry Crater, near Bend Oregon. An interpretive sign about obsidian said that in the '70s an archeologist named Donald Crabtree needed heart surgery. He persuaded his surgeon to make some of the incisions with an obsidian blade, and some with a conventional steel scalpel. The incisions made with obsidian healed better, with much less scar tissue than those made with steel.