DIATOMITE

Diatomite or diatomaceous earth is a silica rock, sedimentary of biogenic origin, formed of fossilized skeletons of millions of unicellular microscopic algae, found in antique water deposits. 

Due to its main properties, it is successfully used as auxiliary filter, insecticide, fertilizer and additive in animal feed, and has also been used as abrasive agent, for metal polishing and in toothpaste.