Metamorphic Rocks
Foliated Rocks
| Slate | |
| Texture: | Foliated / Slatey |
| Degree of Metamorphism: | Low |
| Protolith: | Shale, siltstone, or tuff |
| Minerals present: | None visible! |
| Comments: | - Usually dark grey in color - No visible minerals - Very hard - Layers |
| Phyllite | |
| Texture: | Foliated / Slatey |
| Degree of Metamorphism: | Low, between slate and schist |
| Protolith: | Slate, shale, siltstone, or tuff |
| Minerals present: | Platy minerals not large enough to be identified with the unaided eye |
| Comments: | Glossy sheen and wavy surfaces |
| Schist | |
| Texture: | Foliated / Schistossic |
| Degree of Metamorphism: | Medium |
| Protolith: | Phyllite, slate, shale, siltstone, or tuff |
| Minerals present: | Varies, but commonly include: Muscovite, biotite, chlorite, amphiboles, quartz, garnet, kyanite |
| Comments: | - Medium- to coarse-grained (scaly)
- Platy minerals - May have porphyroblasts |
| Gneiss | |
| Texture: | Foliated / Gneissic |
| Degree of Metamorphism: | High |
| Protolith: | Shale/mudstone, igneous rocks |
| Minerals present: | Varies, but commonly include: Muscovite, quartz, feldspars, biotite, hornblende, garnet, kyanite |
| Comments: | - Medium- to coarse-grained
- Banded appearance - Looks granitic |
| Migmatite | |
| Texture: | Foliated / Gneissic |
| Degree of Metamorphism: | High |
| Protolith: | Partially melted gneiss |
| Minerals present: | Varies, but commonly include: Muscovite, quartz, feldspars, biotite, hornblende, garnet, kyanite |
| Comments: | - Igneous and metamorphic features
- Mineralogy controls behavior. Felsics melt first; mafics remain metamorphic. |