How would you stat up this item
Sand of Elemental Transformation
Aura xx transmutation; CL 7th
Slot none; Price xx; Weight --.
Description
This white sand looks unremarkable. It can be thrown as a ranged touched attack, with a range increment of 10ft. The sand is harmless unless the attack successfully hits an elemental of up to medium sized. The elemental is immediately transformed to an elemental of the same size, but of a different type of the wielders choosing. The change lasts for 7 rounds before the elemental reverts back to its original form. The elemental is not harmed in anyway by this change of form and this process does not provoke attacks of opportunity. If the elemental is an ally of the wielder of the sand the elemental does not get a save, otherwise it can attempt DC 16 fortitude save to negate the effect.
Construction
Requirements Craft Wondrous Item, Elemental body I; Cost xxxx gp