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Matrix identification and geology

The finer-grained material that fills the spaces between larger clasts, crystals, or grains in a rock. In sedimentary rocks, the matrix is the fine-grained material clay, silt, mud deposited along with coarser grains. In igneous rocks, it refers to the groundmass surrounding phenocrysts. A high proportion of matrix relative to framework grains indicates poor sorting or a low-energy depositional environment. Field: petrology. Example: A greywacke sandstone has a matrix content exceeding 15%—this abundance of fine-grained clay and silt matrix distinguishes it from cleaner, better-sorted arenites.. Related terms: Groundmass, Clast, Framework grain, Cement.

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  • Groundmass
  • Clast

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 Matrix mean in geology?
The finer-grained material that fills the spaces between larger clasts, crystals, or grains in a rock. In sedimentary rocks, the matrix is the fine-grained material clay, silt, mud deposited along with coarser grains. In igneous rocks, it refers to the groundmass surrounding phenocrysts. A high proportion of matrix relative to framework grains indicates poor sorting or a low-energy depositional environment.
What is an example of Matrix?
A greywacke sandstone has a matrix content exceeding 15%—this abundance of fine-grained clay and silt matrix distinguishes it from cleaner, better-sorted arenites.
Which earth-science field uses the term Matrix?
Matrix is used in petrology.
Which terms are related to Matrix?
Related terms in this reference are Groundmass, Clast, Framework grain, Cement.

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