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Mudstone identification and geology

A fine-grained sedimentary rock composed predominantly of clay-sized particles <0.004 mm and silt-sized particles 0.004–0.0625 mm , with a massive non-fissile texture. Mudstone is distinguished from shale by its lack of fissility—it breaks into blocky fragments rather than splitting along thin laminae. Mudstones accumulate in low-energy environments including lakes, lagoons, deep oceans, and floodplains. Field: sedimentology. Example: The Queenston Formation of southern Ontario is a red mudstone deposited on a Late Ordovician floodplain, with its massive texture and lack of lamination distinguishing it from the fissile shales above and below.. Related terms: Shale, Siltstone, Claystone, Fissility.

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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
2026-03-30T15:19:42.055955+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 Mudstone mean in geology?
A fine-grained sedimentary rock composed predominantly of clay-sized particles <0.004 mm and silt-sized particles 0.004–0.0625 mm , with a massive non-fissile texture. Mudstone is distinguished from shale by its lack of fissility—it breaks into blocky fragments rather than splitting along thin laminae. Mudstones accumulate in low-energy environments including lakes, lagoons, deep oceans, and floodplains.
What is an example of Mudstone?
The Queenston Formation of southern Ontario is a red mudstone deposited on a Late Ordovician floodplain, with its massive texture and lack of lamination distinguishing it from the fissile shales above and below.
Which earth-science field uses the term Mudstone?
Mudstone is used in sedimentology.
Which terms are related to Mudstone?
Related terms in this reference are Shale, Siltstone, Claystone, Fissility.

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