metamorphic
Rounded quartzite cobble
Quartzite, composed predominantly of recrystallized quartz (SiO₂)
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray-white with rusty pink-brown iron-oxide staining, a dull to sugary sparkle, and no obvious cleavage. Quartz grains are interlocked in a massive texture; the smooth shape is from natural abrasion or tumbling.
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Physical properties
Hardness about 7 Mohs; pale gray-white with rusty pink-brown iron-oxide staining, a dull to sugary sparkle, and no obvious cleavage. Quartz grains are interlocked in a massive texture; the smooth shape is from natural abrasion or tumbling.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized by heat and pressure, commonly during regional metamorphism. The specimen’s specific age and source cannot be determined from the image.
Uses & applications
Used as decorative stone, landscaping gravel, building aggregate, and sometimes as a lapidary material.
Geological facts
Quartzite is generally harder and more resistant to weathering than its sandstone precursor.
Field identification & locations
Look for a dense, hard rock with interlocking quartz grains; it typically scratches glass and does not split readily along bedding. Quartzite occurs worldwide in metamorphic terrains and river or beach gravels.
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