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Chert identification and geology

A hard, dense, microcrystalline or cryptocrystalline sedimentary rock composed almost entirely of silica SiO₂ , usually in the form of chalcedony and microquartz. Chert forms through the diagenetic replacement of host sediments by silica derived from biogenic sources radiolaria, diatoms, sponge spicules or from silica-rich pore fluids. Varieties include flint, jasper, and novaculite. Field: sedimentology. Example: Ribbon cherts in the Franciscan Complex of California consist of thin, alternating layers of radiolarian chert and shale deposited on the abyssal ocean floor and later accreted to the continental margin.. Related terms: Silica, Chalcedony, Flint, Radiolarian.

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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
2026-03-30T15:19:42.127987+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Chert mean in geology?
A hard, dense, microcrystalline or cryptocrystalline sedimentary rock composed almost entirely of silica SiO₂ , usually in the form of chalcedony and microquartz. Chert forms through the diagenetic replacement of host sediments by silica derived from biogenic sources radiolaria, diatoms, sponge spicules or from silica-rich pore fluids. Varieties include flint, jasper, and novaculite.
What is an example of Chert?
Ribbon cherts in the Franciscan Complex of California consist of thin, alternating layers of radiolarian chert and shale deposited on the abyssal ocean floor and later accreted to the continental margin.
Which earth-science field uses the term Chert?
Chert is used in sedimentology.
Which terms are related to Chert?
Related terms in this reference are Silica, Chalcedony, Flint, Radiolarian.

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