Small Obsidian Shard

Small Obsidian Shards are pieces of dark volcanic rock that can be used by Blacksmiths to craft strong armors with anti-magical powers.

Source
This item can be found by mining Small Obsidian Chunks and Large Obsidian Chunks which will sometimes appear after defeating certain mobs inside Ahn'Qiraj. A Mining skill of 305 is required to mine the chunks. Pre-BC the miners had to max their skill (to 300) and have the +5 Mining Enchant, like Skinners had to have Finkle's Skinner in order to skin The Beast.

Blacksmithing

 * Black Grasp of the Destroyer
 * Heavy Obsidian Belt
 * Light Obsidian Belt
 * Jagged Obsidian Shield
 * Obsidian Mail Tunic
 * Thick Obsidian Breastplate