metamorphic
Quartz-rich metamorphic rock, likely mica schist or gneiss
Quartz–feldspar–mica schist/gneiss; commonly containing biotite or muscovite
AI-generated identification · may be incorrectCoarse, strongly foliated texture with silvery mica, white-gray quartz/feldspar, and dark biotite-rich bands. Hardness is approximately 2–3 for mica and 6–7 for quartz; luster ranges from pearly on mica to glassy on quartz, with mica cleavage and no overall crystal cleavage.
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Physical properties
Coarse, strongly foliated texture with silvery mica, white-gray quartz/feldspar, and dark biotite-rich bands. Hardness is approximately 2–3 for mica and 6–7 for quartz; luster ranges from pearly on mica to glassy on quartz, with mica cleavage and no overall crystal cleavage.
Formation & geological history
Formed when clay-rich or granitic protoliths were subjected to intense heat and pressure during regional mountain-building, typically over hundreds of millions to billions of years. The specimen appears weathered and naturally rounded, though exact identification requires a fresh surface or thin section.
Uses & applications
Commonly used as decorative stone, landscaping rock, aggregate, and occasionally building or wall stone; attractive pieces may be collected but are generally not gem-grade.
Geological facts
The glittering flakes are probably mica aligned by metamorphic pressure, producing foliation. Alternating light quartz/feldspar and dark mica layers can indicate gneissic banding.
Field identification & locations
Look for sparkly platy mica, light quartz-rich areas, dark bands, and a layered fabric; it may occur in ancient continental shields and metamorphic mountain belts. A magnet, acid test, and fresh fracture can help distinguish it from altered granite.
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