Obsidian is a volcanic glass with a reputation for being extremely sharp. Some surgeons use obsidian scalpels rather than high-quality steel surgical scalpels.
At the same time, glass blades are used for Microtomes and can even be Manufactured on site.
Is obsidian really sharper than other glasses? If so, what properties make obsidian sharper? Why can't we make special glass for use in scalpels that's as sharp as obsidian?