Phyllite is a low- to intermediate-grade, foliated metamorphic rock.  It forms by the metamorphism of slate.  Phyllite is typically light gray to dark gray to blackish in color.  It has a slightly shiny luster in the light, with slightly wrinkled or crinkled foliation planes.  It is principally composed of microcrystalline mica.


Phyllite (4.5 cm across)




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