metamorphic
Weathered quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), with possible feldspar, mica, and iron-oxide staining
AI-generated identification · may be incorrectHardness about 7 Mohs; gray, white, tan, and rusty-brown coloration with a dull to slightly glassy luster. Massive, nonfoliated texture and no obvious cleavage; exact specific gravity is likely around 2.6–2.7.
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Physical properties
Hardness about 7 Mohs; gray, white, tan, and rusty-brown coloration with a dull to slightly glassy luster. Massive, nonfoliated texture and no obvious cleavage; exact specific gravity is likely around 2.6–2.7.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under heat and pressure during regional metamorphism, commonly during mountain building. Its precise geological age cannot be determined from the photograph.
Uses & applications
Used as durable building stone, aggregate, paving, and decorative material; attractive pieces may be polished for ornamental objects, though this specimen appears ordinary and unprocessed.
Geological facts
Quartzite commonly breaks across quartz grains rather than around them, producing a tough, irregular fracture. Brown zones likely reflect limonite or hematite weathering.
Field identification & locations
Identify it by its granular quartz appearance, exceptional hardness, and resistance to scratching by steel; unlike sandstone, it usually does not crumble along bedding. Common in metamorphic mountain belts worldwide, including the Appalachians, Alps, India, and Brazil.
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