Ask-A-Geologist #6: What term is used for metamorphic rocks with a banded texture?

Hi everyone! Today we have another fabulous question from one of our readers. Today’s question is about metamorphic rocks.

Jason asks:   What term is used for metamorphic rocks with a banded texture?


Hi Jason:  You may be referring to “foliation” which is the aligning of minerals within a metamorphic rock. Foliation occurs when there is a strong pressure applied to the rock in one direction, just like when you put your hands flat together and push. When this pressure is applied, certain minerals, like mica and chlorite, grow with their long direction perpendicular to the pressure. This make the rock look like it has layers.

 

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