Every attack deals additional bonus random elemental damage at a 100% modifier. Spirit procs less often than the other three.
The elemental damage is considered an independent 'hit' on the target. It has an independent chance of being a critical hit or triggering an effect.
Damage of of the elemental damage will match the damage of the skill being used. Eg: If Mighty Blow deals 200% weapon damage, the bonus elemental damage will also be 200%. If Whirlwind deals 70% damage, the bonus damage will also be 70%.
Masterwork procs also benefit form this effect.
Unlike its cousin, the Chromatic Greatsword, the Prismatic Greataxe does not suffer from the 50% modifier to basic physical attacks.