metamorphic
Quartz-rich metamorphic cobble (possibly quartzite)
Quartzite, composed predominantly of recrystallized quartz (SiO₂); identification is tentative from the image
AI-generated identification · may be incorrectGray-white, weathered, rounded cobble with a granular, slightly lustrous surface and reddish-brown staining. Quartz has Mohs hardness 7 and a trigonal crystal structure; the rock appears massive, with no obvious cleavage.
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Physical properties
Gray-white, weathered, rounded cobble with a granular, slightly lustrous surface and reddish-brown staining. Quartz has Mohs hardness 7 and a trigonal crystal structure; the rock appears massive, with no obvious cleavage.
Formation & geological history
If quartzite, it formed when quartz-rich sandstone was compacted and recrystallized under heat and pressure. Its age and original geological setting cannot be determined from the photograph.
Uses & applications
Quartzite is used as crushed aggregate, road stone, building and decorative stone, and occasionally for landscaping or collecting.
Geological facts
Quartzite is typically harder and more resistant to weathering than its sandstone precursor. The visible reddish patches may be iron-oxide staining rather than a distinct mineral feature.
Field identification & locations
Look for a hard, quartz-rich texture and grains that appear fused rather than readily separating like sand; a scratch test or fresh broken surface would help distinguish quartzite from other rocks. Quartzite occurs in metamorphic belts worldwide.
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