Diatomite is a silica mineral composed of fossilized skeletal remains of microscopic single-celled aquatic plants (algae) called diatoms. Over 10,000 species of microscopic algae have been recognized, each one has its own distinct shape and ranging in size from below 5 microns to above 100 microns. Diatomite deposits are of sedimentary origin that is consisting mainly of the accumulation of the skeletons which were formed as the external protective coverage for the aquatic floating algae or diatoms. These skeletons are amorphous hydrated or opaline silica. Normally, the diatomite deposits not only consists of diatom shells, but also contains other sediments like clay, inorganic carbonates, iron oxides, and fine sand. Diatomite has many important industrial applications due to its unique properties, i.e. micronized and sub-micronized porous structure, light-weight, and chemical inertness. These applications include filter aid, functional filler, insulation, catalysis support, and carrier application.