metamorphic
Weathered quartz-rich rock, possibly quartzite or granite fragment
Quartzite (SiO₂-dominant) or altered granitoid; uncertain from image
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; pale cream-gray with brown iron-oxide staining, granular texture, and dull to weakly glassy luster. No clear cleavage is visible; quartz grains appear interlocked, though the small, weathered specimen limits identification.
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Physical properties
Hardness about 6.5–7 Mohs; pale cream-gray with brown iron-oxide staining, granular texture, and dull to weakly glassy luster. No clear cleavage is visible; quartz grains appear interlocked, though the small, weathered specimen limits identification.
Formation & geological history
If quartzite, it formed when quartz-rich sandstone was metamorphosed under heat and pressure, commonly during mountain building; if granitoid, it crystallized from cooling magma. A precise geological age and classification require testing or a clearer specimen view.
Uses & applications
Ordinary pieces have little commercial value; quartzite is used as aggregate, building stone, and decorative stone, while attractive pieces may be collected. It is not visibly gem quality.
Geological facts
Iron oxides commonly produce the tan-brown staining seen on weathered quartz-bearing rocks. A steel file generally fails to scratch quartzite, while glass can be scratched by a fresh edge.
Field identification & locations
Common in many continental mountain belts and sedimentary basins. Field identification requires a fresh surface, hand lens, streak test, and hardness test; acid testing is usually nonreactive unless carbonate minerals are present.
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