Translucent sheet of muscovite mica

“Nodular” habit of biotite mica in an unusual granite - yes, granite.

. #MuseuGeologico in #Lisbon is small but perfectly formed. Contrasting exhibits of #biotite and #musovite micas: muscovite as a translucent sheet c 250x250mm, biotite - wait for it - in discrete nodules within an unusual form of granite, which spall off in lumps as they’re weathered out.