Mystical Skyfire Diamond

A Mystical Skyfire Diamond is a meta gem with a 15% chance to grant 6 seconds of 320 Spell Haste Rating, with a 45 second internal cooldown. The buff given is called focus. The gem can proc off instant casts, but they will not consume focus.

Source
Mystical Skyfire Diamond is crafted by Jewelcrafters with a skill of 365.

The design is a world drop.