MUSCOVITE

[traveler]

I'm looking for a little help with Mica and how it changes with time and geologic conditions.
This first one is just like the text book Muscovite.

This one still looks like mica pieces, but are bundled up in a ball and is pretty fragile.

This has been through some changes.....SHIST?

And here it has been through a lot of changes......GNEISS?

Am I close or way off the mark.

[gemlover]

You are on the right track.

the first book of mica (Muscovite) looks fairly fresh. has not been weathered much.

the second picture appears to be a well weathered rock that held Muscovite as one of its minerals.

Schist is a low grade metamorphic rock where muscovite and/or biotite can be included in the mineral make up of the rock.

Gneiss is a high grade metamorphic rock (more temperature and pressure than low grade), where some mica may have still survived, but the predominate type minerals are now garnet, tourmaline and kyanite.