metamorphic
Weathered quartz-rich rock fragment (possibly iron-stained quartzite)
Quartzite; primarily quartz (SiO₂), with iron-oxide staining and minor accessory minerals
AI-generated identification · may be incorrectHardness about 7 Mohs; tan-brown, granular, and unevenly weathered with a dull to slightly vitreous luster. Quartzite is massive and non-cleavable, with conchoidal to irregular fracture; exact properties are uncertain from the image.
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Physical properties
Hardness about 7 Mohs; tan-brown, granular, and unevenly weathered with a dull to slightly vitreous luster. Quartzite is massive and non-cleavable, with conchoidal to irregular fracture; exact properties are uncertain from the image.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under metamorphic heat and pressure, typically during mountain building. Its age depends on the source sandstone and metamorphic event, commonly ranging from Precambrian to Phanerozoic.
Uses & applications
Used as crushed aggregate, building stone, paving, and decorative material; attractive pieces may be collected but are generally low-value.
Geological facts
Quartzite commonly resists weathering more strongly than surrounding rocks, forming ridges and resistant cobbles. Iron oxides can produce the brown, rusty coloration visible here.
Field identification & locations
Look for a very hard, quartz-granular texture and grains fused across broken surfaces; it should scratch glass and resist a steel knife. Common in metamorphic mountain belts and stream gravels; a streak, acid test, and close inspection are needed to distinguish it from ordinary quartz-rich sandstone.
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