All mystics have access to an additional class skill called Mysticraft, which is used for identifying mystic effects both as they are created and after they are already in place. However, the Spellcraft skill is cross-class for the mystic (as is Mysticraft for the non-mystic). The DCs for identifying mystic effects are the same as those for Spellcraft, with mystic effects counting as one half the sphere total (rounded down) in spell level.
While Spellcraft and Mysticraft are quite different in many ways, they are related skills. A character with five ranks in Mysticraft receives a +2 synergy bonus to Spellcraft. Conversely, five ranks in Spellcraft grants a +2 synergy bonus to Mysticraft.