metamorphic
Quartz-rich metamorphic rock, possibly quartzite
Quartzite; primarily crystalline silicon dioxide (SiO₂), with minor feldspar, mica, or iron oxides
AI-generated identification · may be incorrectHardness about 7 Mohs; gray to whitish with rusty brown staining, granular texture, and glassy to dull luster. Quartzite lacks strong cleavage and commonly breaks irregularly or conchoidally; exact identification is limited by the photograph.
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Physical properties
Hardness about 7 Mohs; gray to whitish with rusty brown staining, granular texture, and glassy to dull luster. Quartzite lacks strong cleavage and commonly breaks irregularly or conchoidally; exact identification is limited by the photograph.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under heat and pressure during regional metamorphism, commonly during mountain-building events. Its age depends on the source sandstone and metamorphic event, ranging from Precambrian to younger rocks.
Uses & applications
Used as crushed stone, aggregate, riprap, paving, and occasionally decorative building stone; attractive specimens may be collected but this example appears common-grade.
Geological facts
Quartzite is generally harder and more resistant to weathering than its sandstone precursor. Iron-oxide staining produces the reddish-brown patches visible here.
Field identification & locations
Likely quartzite if the gray grains are tightly fused and the rock scratches glass; sandstone if grains are visibly loose or gritty. Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, and Precambrian shields.
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