Obsidian Sphere (Best Available)

Obsidian is a type of naturally occurring volcanic glass, produced when lava cools rapidly with minimal crystal growth. It has a high silica content, and upon rapid cooling, it results in a natural glass. The brittle quality of Obsidian lends itself to be sharpened, just as shards of glass are extremely sharp. For this reason, Obsidian has been used to make cutting and piercing tools, such as arrowheads and experimentally as surgical blades.