To be honest, the obsidian head is sharper than the head you have pictured below. Obsidian and flint can be napped sharper than any metal. You can actually nap obsidian to a beval width of 1 atom. Which is much sharper than any metal. The reason many do not use stone heads is because they are very hard to nap and get balanced. And to buy good obsidian heads, you will spend much more money than you will on steal heads. Ive seen them used many times.