metamorphic
Mica-rich metamorphic rock, likely phyllite or schist
Quartz–mica schist/phyllite; chiefly muscovite or biotite mica with quartz and feldspar
AI-generated identification · may be incorrectVisible platy, glittering mica flakes give a foliated texture and pearly to vitreous luster; mica hardness is about 2–3 Mohs, while quartz is 7. Color is silvery-gold to brown-gray, with excellent cleavage in the mica and low-to-moderate specific gravity (~2.7–2.9).
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Physical properties
Visible platy, glittering mica flakes give a foliated texture and pearly to vitreous luster; mica hardness is about 2–3 Mohs, while quartz is 7. Color is silvery-gold to brown-gray, with excellent cleavage in the mica and low-to-moderate specific gravity (~2.7–2.9).
Formation & geological history
Formed when clay-rich sedimentary rock was buried, heated, and compressed during regional metamorphism, commonly during mountain building. The image alone cannot establish its geological age; such rocks range from Precambrian to recent orogenic belts.
Uses & applications
Used locally as decorative stone, aggregate, fill, and landscaping material; attractive mica-rich pieces may be collected, but this specimen is not gem-grade.
Geological facts
Gold-colored flakes may be muscovite, while darker bronze-brown flakes may be biotite; lighting can make either appear golden. Strong foliation and sparkling cleavage surfaces distinguish it from massive granite.
Field identification & locations
Common in metamorphic belts worldwide, including the Appalachians, New England, Scandinavia, India, and Brazil. Scratch-test mica-rich surfaces gently, inspect for flexible flakes, and distinguish from pyrite by the sheet-like cleavage and lack of cubic crystals.
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