Perma-Guard OMRI certified Diatomaceous Earth Fossil Shell Flour is the purest food grade fresh water amorphous silica diatomaceous earth available. Perma-Guard is derived from fossilized diatoms remains. Diatoms are prehistoric and form from the depositing of microscopic algae-like plant remains into the earth’s surface. These chalky remains are usually found in the form of a thick, white, siliceous powder known as diatomaceous earth. An excellent all natural insecticide!