metamorphic
Iron-stained quartzite or quartz-rich rock fragment
Quartzite; predominantly silicon dioxide (SiO₂), with iron-oxide staining
AI-generated identification · may be incorrectHardness about 7 Mohs; gray-white, brown to reddish-brown surfaces, vitreous to dull luster, and massive granular texture without obvious cleavage. The angular fragment appears dense and resistant, though the image cannot confirm mineral grains or internal structure.
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Physical properties
Hardness about 7 Mohs; gray-white, brown to reddish-brown surfaces, vitreous to dull luster, and massive granular texture without obvious cleavage. The angular fragment appears dense and resistant, though the image cannot confirm mineral grains or internal structure.
Formation & geological history
Likely formed when quartz-rich sandstone recrystallized under heat and pressure, commonly during regional metamorphism; its precise geological age is indeterminate from the photograph. Brown coloration probably comes from hematite or limonite weathering.
Uses & applications
Quartzite is used as crushed stone, road aggregate, building stone, countertops, and decorative material; attractive pieces may be collected but this fragment has little commercial value.
Geological facts
Quartzite commonly breaks across quartz grains rather than around them and can scratch ordinary glass. Iron staining often develops along fractures or weathered surfaces.
Field identification & locations
Look for a very hard, sugary or glassy texture and inability to scratch it with a steel knife; acid should not fizz unless carbonate minerals are present. Common in metamorphic mountain belts worldwide.
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