Here's why:
* Foliation: This refers to the parallel alignment of mineral grains within the rock, giving it a layered or banded appearance. This alignment is caused by pressure and heat during metamorphism.
* Banded or Striped: The bands are formed by different minerals aligning in layers, creating distinct stripes or bands.
Examples of foliated metamorphic rocks include:
* Slate: A fine-grained, low-grade metamorphic rock with a smooth, slaty cleavage.
* Schist: A medium-grade metamorphic rock with a more pronounced foliation, often with visible mineral grains.
* Gneiss: A high-grade metamorphic rock with a distinct banding of light and dark minerals.
Non-foliated metamorphic rocks:
In contrast to foliated rocks, non-foliated metamorphic rocks do not have a banded or striped appearance. They are formed when the pressure during metamorphism is equal in all directions, or when the minerals are not easily aligned. Examples include marble and quartzite.
