The fossil remains of diatoms, diatomite or Kieselguhr, have a range of uses, including as a filtration aid, a mild abrasive in toothpaste and metal polish, a mechanical insecticide, an absorbent for liquids, cat litter and as a component of dynamite.

Because different species have particular ecological requirements and distributions, diatoms are used in water quality analysis, e.g. Water Framework Directive, and are also useful to forensic scientists.