Obsidian

Obsidian is also called natural glass or volcanic glass. It is hard, glossy, and black, and was often chipped into knives and arrowheads, but the finer grades of stone were usually polished and smoothed to remove sharp edges. Obsidian was often carved into figurines, including the magical obsidian steed. Low quality obsidian was called pitchstone and had a rougher surface, a dull appearance, and a lower price. A typical specimen had a base value of 10 gp.

Realmslore
Blacksmoke obsidian is often found and sold in Tashalan bazaars.