metamorphic
Weathered quartzite or quartz-rich metamorphic rock
Quartzite, predominantly microcrystalline SiO₂, possibly with mica, feldspar, and iron-oxide staining
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray, cream, tan, and bluish-gray; generally dull to vitreous luster with interlocking granular texture and no obvious cleavage. Dense and resistant, though this specimen is heavily weathered and fractured.
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Physical properties
Hardness about 7 Mohs; pale gray, cream, tan, and bluish-gray; generally dull to vitreous luster with interlocking granular texture and no obvious cleavage. Dense and resistant, though this specimen is heavily weathered and fractured.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under heat and pressure during regional metamorphism, commonly hundreds of millions to billions of years ago. Surface oxidation and weathering produced the tan-brown staining.
Uses & applications
Used as crushed stone, road aggregate, building stone, paving, countertops, and decorative material; this rough piece has little jewelry value.
Geological facts
Quartzite commonly breaks across grains rather than around them, unlike sandstone, and can scratch ordinary glass. The blue-gray areas may reflect mica or other metamorphic minerals.
Field identification & locations
Likely quartzite if a fresh edge is sugary and crystalline and the rock scratches glass; sandstone would show looser grains and crumble more readily. Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, Scandinavia, and India.
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