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Foliation identification and geology

Any planar structural feature in a metamorphic rock produced by the preferred alignment of minerals, compositional layering, or closely spaced fractures. Types of foliation include slaty cleavage very fine-grained , phyllitic sheen, schistosity visible aligned platy minerals , and gneissic banding alternating light and dark compositional bands . Foliation develops perpendicular to the maximum compressive stress direction. Field: petrology. Example: Garnet-mica schist from the Scottish Highlands displays well-developed schistosity defined by aligned muscovite and biotite wrapping around porphyroblastic garnet crystals.. Related terms: Schistosity, Gneissic banding, Slaty cleavage, Lineation.

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  • Schistosity
  • Lineation

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
2026-03-30T15:19:41.999576+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 Foliation mean in geology?
Any planar structural feature in a metamorphic rock produced by the preferred alignment of minerals, compositional layering, or closely spaced fractures. Types of foliation include slaty cleavage very fine-grained , phyllitic sheen, schistosity visible aligned platy minerals , and gneissic banding alternating light and dark compositional bands . Foliation develops perpendicular to the maximum compressive stress direction.
What is an example of Foliation?
Garnet-mica schist from the Scottish Highlands displays well-developed schistosity defined by aligned muscovite and biotite wrapping around porphyroblastic garnet crystals.
Which earth-science field uses the term Foliation?
Foliation is used in petrology.
Which terms are related to Foliation?
Related terms in this reference are Schistosity, Gneissic banding, Slaty cleavage, Lineation.

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