Black Diamond

Black Diamond is a raw gem used in some crafting professions and quests.

Source
It can be mined from Dark Iron Deposits and drops from mobs in Blackrock Depths.

As a crafting reagent
Black Diamond is used in the following recipes:
 * Blacksmithing
 * Darkrune Helm


 * Enchanting


 * Enchant Cloak - Subtlety


 * Jewelcrafting
 * Figurine - Black Diamond Crab
 * Prismatic Black Diamond


 * Leatherworking
 * Mongoose Boots

As a quest item
Black Diamond is needed for the following quests:
 * Libram of Voracity (quest)
 * Libram of Constitution (quest)
 * Libram of Tenacity (quest)
 * Libram of Rumination (quest)
 * Libram of Resilience (quest)