Rock of the week 4: Retrograde metamorphism from the Grenville Province

In this video we see a rock formed in the base of a mountain chain that approximately a billion years ago was higher than the Himalayas. Under these conditions garnet formed, as the pressure was lessened later biotite replaced some of the garnet.
key words: Mountain building, geology, garnet, biotite, Grenville,

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Great job

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Thanks