Mylonite identification and geology

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• Phyllite
• Schist

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

2026-03-30T14:39:17.066924+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.
• Can you identify my rock or mineral? — U.S. Geological Survey. Identification limitations and routes to in-person professional verification.

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Common questions

What is Mylonite?

Fine-grained, banded rock formed by ductile deformation along fault zones at depth. Grain size reduction by dynamic recrystallization.

How can you identify Mylonite?

Compare several properties rather than relying on colour alone. This entry records rock type: Metamorphic Deformational; texture: Mylonitic fine, streaked; grain size: Very fine to fine; common minerals: Variable depends on protolith, Quartz ribbons, Feldspar porphyroclasts. Confirm an important identification with additional field tests or qualified laboratory work.

How does Mylonite form?

Forms by ductile shearing in fault zones at depths where rocks deform plastically rather than brittlely.

Where is Mylonite commonly found?

Found along major fault zones and shear zones worldwide; Alps, Himalayas, Appalachians.

What is Mylonite commonly confused with?

Mylonite may be confused with Phyllite, Schist, Fault Gouge. Compare multiple diagnostic properties because colour and surface appearance can overlap.