SRD:Magic Aura

You alter an item’s aura so that it registers to detect spells (and spells with similar capabilities) as though it were nonmagical, or a magic item of a kind you specify, or the subject of a spell you specify.

If the object bearing magic aura has identify cast on it or is similarly examined, the examiner recognizes that the aura is false and detects the object’s actual qualities if he succeeds on a Will save. Otherwise, he believes the aura and no amount of testing reveals what the true magic is.

If the targeted item’s own aura is exceptionally powerful (if it is an artifact, for instance), magic aura doesn’t work.

Note: A magic weapon, shield, or suit of armor must be a masterwork item, so a sword of average make, for example, looks suspicious if it has a magical aura.

Focus: A small square of silk that must be passed over the object that receives the aura.