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Stone Science

Metamorphic rocks (scientific)

Scientific terms for metamorphism: protolith, grade, index minerals, and fabric (foliation/lineation).

Classification

How metamorphic rocks are named

Names reflect fabric + mineral assemblage + protolith when known.

Protolith

The original rock before metamorphism (e.g., shale → slate/phyllite/schist; limestone → marble).

Metamorphic grade

Low to high grade reflects temperature/pressure conditions and mineral changes.

Index minerals

Minerals that indicate conditions (e.g., chlorite, garnet, staurolite, kyanite, sillimanite).

Fabric terms

Foliation, schistosity, gneissic banding, lineation; non-foliated textures like granoblastic.

Metamorphic fabrics

Foliation and banding are key scientific descriptors for metamorphic rocks.

Schist outcrop showing foliation Weathered rock surface with mineral vein Granite texture for comparison with metamorphic banding Mineral macro texture in gold and taupe tones
Schist outcrop showing foliation Weathered rock surface with mineral vein Granite texture for comparison with metamorphic banding Mineral macro texture in gold and taupe tones
Schist outcrop showing foliation Weathered rock surface with mineral vein Granite texture for comparison with metamorphic banding Mineral macro texture in gold and taupe tones
Schist outcrop showing foliation Weathered rock surface with mineral vein Granite texture for comparison with metamorphic banding Mineral macro texture in gold and taupe tones
Schist outcrop showing foliation Weathered rock surface with mineral vein Granite texture for comparison with metamorphic banding Mineral macro texture in gold and taupe tones
Schist outcrop showing foliation Weathered rock surface with mineral vein Granite texture for comparison with metamorphic banding Mineral macro texture in gold and taupe tones

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