Phyllite

Phyllite is from scientific Latin and means "leaf-stone." Phyllite is a medium-gray stone, but here sunlight reflects blindingly off its finely wavy face.

Phyllite is one step beyond slate in the chain of metamorphism. Whereas slate has a light sheen from tiny grains of mica, graphite, chlorite and similar minerals, phyllite fairly glitters because with further heat and pressure, the reflective grains grow more abundant and join each other. And whereas slate usually breaks in very flat sheets, phyllite tends to have a corrugated cleavage.

This rock has nearly all of its original sedimentary structure erased, although some of its clay minerals persist. Further metamorphism will convert all of the clays into micas, along with quartz and feldspar. At that point, phyllite becomes schist.

For more photos see the Metamorphic Rocks Gallery.

Fossils
Geologic Features and Processes
Glaciers and Ice
Landforms
Minerals
Rocks
Geology and Society