Phyllite
Image: James St. John (CC BY 2.0)
Mineral NamePhyllite
Chemical FormulaA rock composed primarily of fine-grained micas (muscovite, chlorite), quartz, and often feldspar.
Mohs Hardness2
Streak ColorWhite to light gray
CleavageExcellent phyllitic cleavage (foliation), often wavy or crenulated
FractureUneven to splintery
Specific Gravity2.65
Colorsgray, silvery-gray, greenish-gray, reddish-brown
TransparencyOpaque
Type LocalityNewfound Gap Road roadcut, Great Smoky Mountains, Tennessee, USA (Anakeesta Formation)
Mineral GroupMetamorphic rock
Usesbuilding material, decorative stone, flagstones
Associated Mineralsquartz, muscovite, chlorite, sericite, biotite
Raritycommon
Description
This image displays a fine-grained, foliated metamorphic rock with a distinct wavy or crenulated texture, exhibiting silvery-gray bands intermixed with reddish-brown and orange-brown weathered sections.
Geological Context
Phyllite forms from the low-grade regional metamorphism of shale or mudstone, typically in ancient ocean trenches or orogenic belts, as seen in the Neoproterozoic Anakeesta Formation of the Ocoee Supergroup.
