The main compound in the deadly crystal veins of the plane of Salt, rock salt carries great purification and defensive power against darker entities.
When a single handful is lain in a ring of radius up to 10 feet, it functions as a natural magic circle against evil spell. The spell has unlimited duration so long as the ring remains unbroken, but a break of any size immediately cancels the spell. Hedged entities cannot interfere directly with the ring by any means, including spells and spell-like abilities, but they may interact via indirect means through manipulation of their environment. A ring of rock salt can be recollected and reused as often as need be.
More directly, a handful can be thrown at an outsider or undead of evil alignment, having the same effect as a holy smite spell at CL 10. However, using rock salt in this manner causes it to be instantly consumed, losing all innate qualities and becoming nothing but normal salt.