Zeobrite is an all-natural volcanic mineral rock known as zeolite. Zeolites are formed over millions of years creating a very unique micro-porous structure. After we mine the rock, it goes through our processing plant of various crushers and screening sleeves to acheive the correct particle size for use in water filtration. Viewing individual particles under an electron-scanning microscope reveals a structure of cavities and pore spaces similar to the appearence of a sponge. This micro-porous structure provides a tremendous amount of available surface area for filtering very fine suspended particles from your pool water. If one tablespoon of Zeobrite granules were unfolded to expose all of the available surface area, the exposed surface would cover an entire football field.