The Open Palm is an essence gem which grants a large bonus to Spirit and a moderate bonus to Mind. As its name suggests, it is exclusive to followers of the Way of the Open Palm — there is no exact equivalent for the Way of the Closed Fist, with the closest counterpart (called The Closed Fist) affecting different scores. It is not the same as the gem called the Way of the Open Palm.
In-game description: "In accordance with one's own spirit and the way of the Heavens, the Open Palm is at peace with nature. This ultimate harmony gives mastery over one's self and attunement with the flow of fate."