Diatomite is a soft, siliceous sedimentary rock composed mainly of the fossilized remains of diatoms, a type of microscopic algae. It is highly porous and has a wide range of industrial applications, including filtration, insulation, and as a lightweight aggregate. Diatomite is important in paleoenvironmental studies, as it provides a record of past climatic and ecological conditions.
Reference: Round, F. E., Crawford, R. M., & Mann, D. G. (1990). “The Diatoms: Biology and Morphology of the Genera.” Cambridge University Press.