metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with feldspar, mica, and iron-oxide impurities
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray-green to white, with a granular sugary texture and dull to vitreous luster. Quartz grains are tightly interlocked, producing indistinct cleavage and conchoidal to irregular fracture; specific gravity about 2.6–2.7.
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Physical properties
Hardness about 7 Mohs; pale gray-green to white, with a granular sugary texture and dull to vitreous luster. Quartz grains are tightly interlocked, producing indistinct cleavage and conchoidal to irregular fracture; specific gravity about 2.6–2.7.
Formation & geological history
Formed when quartz-rich sandstone was buried and recrystallized under heat and pressure, commonly during regional metamorphism. Its exact geological age cannot be determined from the photograph and depends on the source formation.
Uses & applications
Used as crushed stone, road aggregate, railroad ballast, refractory silica, and building or facing stone; attractive pieces may be collected but this specimen does not appear gem-quality.
Geological facts
Quartzite is usually harder and more resistant than its parent sandstone, and it commonly preserves faint sedimentary layering or iron-stained bands despite recrystallization.
Field identification & locations
Identify it by testing whether individual grains and the rock itself resist a steel knife; quartzite typically scratches glass and does not fizz with dilute hydrochloric acid. Common in mountain belts worldwide, including the Appalachians, Rocky Mountains, Alps, and India.
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