Fine-grained clastic rock similar to shale but lacking fissility. Breaks into blocky fragments rather than thin sheets. Texture: Fine-grained, massive. Rock type: Sedimentary Clastic. Grain size: Clay to silt. Minerals present: Clay minerals, Quartz, Feldspar. Formation: Forms from compaction of mud in quiet water environments. Distinguished from shale by lack of fissility. Common geological settings: Worldwide; common in floodplain, lacustrine, and marine sedimentary environments. Common look-alikes and related entries: Shale, Siltstone, Claystone.
Shale vs Mudstone — Compare observable properties and safer field tests.
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
2026-03-30T14:38:19.100181+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.
Fine-grained clastic rock similar to shale but lacking fissility. Breaks into blocky fragments rather than thin sheets.
How can you identify Mudstone?
Compare several properties rather than relying on colour alone. This entry records rock type: Sedimentary Clastic; texture: Fine-grained, massive; grain size: Clay to silt; common minerals: Clay minerals, Quartz, Feldspar. Confirm an important identification with additional field tests or qualified laboratory work.
How does Mudstone form?
Forms from compaction of mud in quiet water environments. Distinguished from shale by lack of fissility.
Where is Mudstone commonly found?
Worldwide; common in floodplain, lacustrine, and marine sedimentary environments.
What is Mudstone commonly confused with?
Mudstone may be confused with Shale, Siltstone, Claystone. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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