metamorphic
Weathered schist or phyllite
Micaceous metamorphic rock, commonly quartz–mica schist (quartz + muscovite/biotite)
AI-generated identification · may be incorrectTypically gray, tan, or rusty brown from iron-oxide weathering; foliated, sparkly, and splits along mica-rich planes. Hardness is about 2–7 depending on mica versus quartz; luster ranges from silky to glittery, with platy crystals and weak-to-good foliation.
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Physical properties
Typically gray, tan, or rusty brown from iron-oxide weathering; foliated, sparkly, and splits along mica-rich planes. Hardness is about 2–7 depending on mica versus quartz; luster ranges from silky to glittery, with platy crystals and weak-to-good foliation.
Formation & geological history
Formed when shale or mudstone underwent regional metamorphism, realigning clay minerals into mica and developing foliation; commonly Paleozoic to Precambrian, though age depends on locality.
Uses & applications
Used locally as building stone, wall rock, roofing/slabs, aggregate, and landscaping material; attractive micaceous pieces may be collected but are generally low value.
Geological facts
The rusty central band likely reflects oxidation of iron-bearing biotite or sulfide minerals. Strong foliation and visible mica distinguish it from ordinary sandstone or granite.
Field identification & locations
Common in mountain belts and exposed metamorphic terrains worldwide, including the Appalachians, Alps, Himalaya, and Scandinavian Shield. Check for glittering mica flakes and layers that separate into sheets; a field photo alone cannot securely distinguish schist from phyllite.
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