Obsidian

Obsidian is also called natural glass or volcanic glass. Obsidian is hard, glossy, and black, and is often chipped into arrowheads, but the finer grade of stone is usually polished and smoothed. Obsidian can be carved into figurines, including the magical obsidian steed. Low quality obsidian is called pitchstone and has a rougher surface, a dull appearance, and a lower price. A typical specimen has a base value of 10gp.