Burning Essence is an essence gem which grants moderate bonuses to Spirit and Mind. It does not have an alignment requirement, unlike the Gem of Pure Flame and the Gem of Black Flame (which are otherwise identical).
In-game description: "Burning Essence channels elemental flame to sharpen the mind of its wearer and to strengthen the ability to channel chi. Unlike similar gems that channel elemental fire, this essence gem burns with all aspects of the flame, both creative and destructive. It may be used regardless of the wearer's philosophy."