Diatomite is white, loose or choke-like, sometimes smoothly stratified or slaty sediment made from piling up the frame of diatomaceous algae. They have variable forms: needle, rod, disc, triangle and/or quadrangle. Algae live both in salted and fresh water.
They extract the silica required to build up their frames from the water, so the vast majority of utilisable diatomite reserves are connected to vulcanic regions. Silica relatively easily dissolves from vulcanic glass and tuff at the hydrolitic disintegration of feldspar, and silica is released at the mineralisation. Under these circumstances resupply of the silica is secured, so the life-conditions of diatomaceous algae.
During their life algae molt their armours. Whit the change of biotope they may perish in masses. In addition to this diatomacae serve as main source of food for many species. Silica armor as non-digestable material goes to the sludge. These factors result in the piling up of diatomaceous armor, and creation of even more than 10 meter wide diatomite sediment.
Physical characteristics of diatomite can be origined from special structure of silica armor. Its porosity is very high and its specific weight is low. Specific weight is 2.1-2.2 g/cm3. Its melting point is about 1,610-1,750ºC. It is resistant to acids, dissolves only in hydrofluoric acid. If annealed in aery environment (600-800 ºC) organic materials burn.