Metamorphic rocks are formed from the transformation of existing rock types under high temperature and pressure conditions. Their characteristics include:

### Characteristics:
1. **Texture**: They often display a foliation (layered appearance) or a non-foliated structure.
2. **Mineral Composition**: Common minerals include quartz, feldspar, mica, and amphibole.
3. **Hardness**: Generally harder and more durable than their parent rocks.
4. **Color Variations**: Can range widely in color due to different mineral compositions.
5. **Cohesion**: Increased density and strength compared to parent rocks.

### Classification:
1. **Foliated Metamorphic Rocks**: Characterized by a layered or banded appearance.
– Examples:
– Slate (from shale)
– Schist (from shale or granite)
– Gneiss (from granite or sedimentary rocks)

2. **Non-foliated Metamorphic Rocks**: Do not exhibit layering and have a more uniform texture.
– Examples:
– Marble (from limestone)
– Quartzite (from sandstone)
– Hornfels (from various parent rocks)

These classifications help in understanding the conditions of formation and the properties of the rocks.