- a fine siliceous earth composed chiefly of the cell walls of diatoms: used in filtration, as an abrasive, etc.
- a soft very fine-grained whitish rock consisting of the siliceous remains of diatoms deposited in the ocean or in ponds or lakes. It is used as an absorbent, filtering medium, insulator, filler, etcSee also diatomaceous earth
- an unconsolidated form of diatomiteAlso called: kieselguhr
- A powder made of the desiccated shells of diatoms, used as a filtering agent, adsorbent, and abrasive in many chemical operations.
- A fine, light-colored, friable sedimentary rock consisting mainly of the silica-rich cell walls of diatoms. Diatomite forms both in lacustrine and marine environments. It is used in industry as a filler, filtering agent, absorbent, abrasive, and insulator.