This is obtained from the last encounter in Dragon Soul--Madness of Deathwing on both normal and heroic difficulty (not LFR). Upon defeating either encounter, every player receives one of these in their currency tab.

These are then redeemed from Dasnurimi for Elementium-Coated Geode. This will always contain an uncut epic gem: Shadow Spinel, Lava Coral, or Queen's Garnet.