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Diatomite identification and geology

Diatomite rock reference specimen

Very light, porous sedimentary rock composed of microscopic diatom siliceous algae frustules. Texture: Fine-grained, porous. Rock type: Sedimentary Biogenic. Grain size: Microscopic. Minerals present: Amorphous silica opal. Formation: Accumulates from the settling of diatom frustules in marine or lacustrine environments with high silica availability. Common geological settings: California Lompoc , Denmark, China, Australia; found in marine and lacustrine settings. Common look-alikes and related entries: Chalk, Pumice, Tripoli.

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  • Previous: Diamictite — Non-genetic term for poorly sorted rock with clasts of various sizes in a fine matrix. May be glacial, volcanic, or mass-flow.
  • Next: Diorite — Coarse-grained intrusive igneous rock intermediate between granite and gabbro. Contains plagioclase, hornblende, and biotite.
  • Chalk
  • Pumice

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T14:37:24.729794+00:00
Review status
Published; not independently peer-reviewed
  • Rocks — U.S. National Park Service. Authoritative overview of rock groups, the rock cycle, and geologic processes.
  • Can you identify my rock or mineral? — U.S. Geological Survey. Identification limitations and routes to in-person professional verification.

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Common questions

What is Diatomite?
Very light, porous sedimentary rock composed of microscopic diatom siliceous algae frustules.
How can you identify Diatomite?
Compare several properties rather than relying on colour alone. This entry records rock type: Sedimentary Biogenic; texture: Fine-grained, porous; grain size: Microscopic; common minerals: Amorphous silica opal. Confirm an important identification with additional field tests or qualified laboratory work.
How does Diatomite form?
Accumulates from the settling of diatom frustules in marine or lacustrine environments with high silica availability.
Where is Diatomite commonly found?
California Lompoc , Denmark, China, Australia; found in marine and lacustrine settings.
What is Diatomite commonly confused with?
Diatomite may be confused with Chalk, Pumice, Tripoli. Compare multiple diagnostic properties because colour and surface appearance can overlap.

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