What is a diatomite in geology ?

Diatomite : definition

Diatomite is a clear and porous sedimentary rock, formed by the accumulation of siliceous shells of unicellular algaen : diatomea (photo on the right - © Larousse). These algae live in warm waters, often in a volcanic environment. They can harbor insect and plant fossils.

Diatomite is used as an abrasive, as an absorbent or as an inert material to stabilize dynamite. It is also a rock widely used in cinema because of its very low specific gravity (0.2 to 0.3). The names of tripoli, kieselguhr or "fossil flour" also designate diatomite.