Heart of the Ancients

The Heart of the Ancients can be found in Grizzly Hills.

Quests

 * Heart of the Ancients (quest)
 * My Heart is in Your Hands

Item source
This item is a reward from Heart of the Ancients (quest).

As noted in the tooltip, the inventory item is not the questgiver, the world object is. (Despite the fact that you apparently just picked up the gem...)