Obsidian

Unit value: 250 gp Armor: While wearing a non-magical medium or heavy armor (non-hide) made with obsidian, when an enemy grapples you, it takes 1d4 slashing damage. Weapons: A non-magical weapon made with obsidian deals an additional 1d4 slashing damage. It's also used for crafting the sword of sharpness.

This black to deep purple glass-like stone is known to be very sharp.

Type