metamorphic
Weathered quartz-rich metamorphic rock (probable quartzite)
Quartzite; predominantly microcrystalline quartz (SiO₂), with possible mica, feldspar, and iron-oxide impurities
AI-generated identification · may be incorrectHardness about 7, gray to tan, dull-to-slightly sparkling luster, massive granular texture, no obvious cleavage, and typically high specific gravity around 2.6. The rusty yellow-brown areas likely reflect iron-oxide weathering or attached altered material.
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Physical properties
Hardness about 7, gray to tan, dull-to-slightly sparkling luster, massive granular texture, no obvious cleavage, and typically high specific gravity around 2.6. The rusty yellow-brown areas likely reflect iron-oxide weathering or attached altered material.
Formation & geological history
Quartzite forms when quartz-rich sandstone is recrystallized under heat and pressure during regional metamorphism; its age depends on the original sandstone and could range from Precambrian to much younger. The surface is strongly weathered and may include a contrasting matrix or coating.
Uses & applications
Used as crushed aggregate, road stone, slabs, wall stone, and occasionally as a decorative or lapidary material; this rough specimen has little jewelry value.
Geological facts
Quartzite commonly breaks across grains rather than around them, producing very hard, sharp fragments. It can be confused with quartz-rich sandstone, but quartzite generally lacks visible pore spaces and resists scratching by steel.
Field identification & locations
Common in metamorphic mountain belts worldwide, including the Appalachians, Alps, Scandinavia, India, and western North America. A steel file should fail to scratch fresh quartz-rich surfaces; acid typically produces no reaction.
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