metamorphic
Mica-rich quartzite or schist
Quartz–mica metamorphic rock; chiefly SiO₂ with muscovite/biotite mica and minor feldspar
AI-generated identification · may be incorrectHardness about 6–7 for quartz, with distinctly softer mica; gray, silvery, cream, and pink colors, glassy to pearly luster, and visible flaky crystals. The specimen appears foliated and sparkly, with irregular cleavage dominated by mica rather than a uniform crystal structure.
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Physical properties
Hardness about 6–7 for quartz, with distinctly softer mica; gray, silvery, cream, and pink colors, glassy to pearly luster, and visible flaky crystals. The specimen appears foliated and sparkly, with irregular cleavage dominated by mica rather than a uniform crystal structure.
Formation & geological history
Likely formed when quartz-rich sandstone or clay-rich sediment was subjected to elevated pressure and temperature during regional metamorphism, commonly hundreds of millions to billions of years ago. Exact age and identification require thin-section or laboratory analysis.
Uses & applications
Used locally as crushed aggregate, building stone, decorative stone, and occasionally dimension stone; attractive pieces may be collected but are generally not gem material.
Geological facts
Mica flakes produce the bright glitter and can split into thin elastic sheets, while quartz forms the hard, granular framework. Pink areas may indicate feldspar or iron staining.
Field identification & locations
Look for abundant interlocking quartz grains, visible mica flakes, foliation, and a poor response to dilute acid; it will scratch glass but mica-rich surfaces may flake. Common in metamorphic belts worldwide, including the Appalachians, Canadian Shield, and mountain regions.
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