Diatomite is a fossilised mineral of vegetable origin. It is the accumulation of an enormous number of fossil diatoms.

Diatoms are single cell plants of microscopic size. There are many varieties that live in both freshwater lakes and saltwater oceans, staying close to the surface where they form part of the abundant plankton. Alive, they are at the base of the food chain. Dead, they leave a tiny
skeleton known as a frustule.

Whereas most other plants use solar energy to synthesise cellulose for their cell walls, the diatom extracts amorphous silica from the water, building for itself what amounts to an elegant, but strong shell with highly symmetrical perforations.

Diatoms reproduce themselves in bi-cell divisions every few hours and it has been estimated that a single diatom could produce up to 1,000,000,000 diatoms.

In its natural (milled) state, the individual diatoms are extremely small and would form a very fine (low permeability) filter-cake, which would be too ‘slow’ for most filtration applications. To create larger particles, the diatoms are fused together at high temperatures. These larger
particles are then classified, according to their specification.

Large deposits are now open-cast mined in the USA, Northern Europe and Iceland.