Diatomaceous earth forms in marine and freshwater systems where diatom formation, diatom preservation, and deposition processes combine to produce diatom deposits. Diatomaceous earth formation appears to be particularly prevalent during the Miocene, Pliocene-Pleistocene, and early-to-middle Holocene. These extensive natural deposits are often exploited commercially due to the high silica content and fine-grained structure that imparts properties to diatomaceous earth deposits. These deposits are of marine or freshwater origin and are mined in both the northern and southern hemispheres. Commercial mining of diatomaceous earth began less than 200 years ago, but diatomaceous earth has been used in construction products since at least the first millennium BC. Diatomaceous earths have a variety of modern uses, and they have recently been shown to be a useful additive to improve the quality of cement and other construction products. Their value as proxies for past environmental changes and indicators of evolutionary trends in diatoms has been underestimated.
diatomite
The use of diatomaceous earth in the manufacturing process and as an ingredient in finished products has potential uses in forensic investigations. In addition, other raw materials may also contain diatoms, such as diatomaceous earth used to make ceramics. For example, pottery, tile or bricks may retain diatoms where they were fired at lower temperatures. However, the most important diatomaceous earth raw material is diatomaceous earth. This is a porous, low-density sedimentary rock formed by the accumulation and compaction of diatoms, which make up 90% or more of the dry weight of the rock. The physical properties of diatomite diatomaceous earth have led to its use in many commercial applications, most commonly for liquid filtration or as a filler, for example, in paints. Other uses of diatomaceous earth include insulation (refractory bricks), fine abrasives (in some toothpastes and polishes), and as an insecticide. Freshwater and marine diatomaceous earths are mined around the world and range in age from the Late Cretaceous to the Holocene, so the assemblages of diatoms present can vary widely. The total world production of diatomaceous earth is estimated to be about 2 million tons per year