Phyllite
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Mineral NamePhyllite
Chemical FormulaPhyllite is a metamorphic rock composed primarily of fine-grained mica (sericite, muscovite, chlorite) and quartz, with variable accessory minerals.
Mohs Hardness3
Streak ColorWhite to light grey
CleavageExcellent phyllitic cleavage (foliation), allowing it to split into thin, wavy sheets.
FractureUneven to splintery across foliation.
Specific Gravity2.75
Colorsgrey, greenish-grey, brownish-grey, silvery
TransparencyOpaque
Type LocalitySrinagar Garhwal, India
Mineral GroupMetamorphic Rock (specifically, a foliated metamorphic rock)
Usesroofing tiles, decorative stone, landscaping, flagstone
Associated Mineralsquartz, muscovite, chlorite, sericite, biotite
Raritycommon
Description
The image displays a dark grey to brownish-grey phyllite outcrop exhibiting strong, wavy foliation and tight folds, indicative of intense deformation. A small tool provides scale against the layered rock surface.
Geological Context
Phyllite forms from the regional metamorphism of fine-grained sedimentary rocks like shale or slate under conditions of low to medium temperature and pressure, typically in convergent plate boundaries.
