metamorphic
Quartzite (River Cobble)
Metamorphic Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: reddish-brown, tan, and yellowish-brown with iron oxide staining; Luster: vitreous to dull/sugary; Structure: granular, interlocking quartz crystals; Cleavage: none.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull/sugary
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Physical properties
Hardness: 7 on Mohs scale; Color: reddish-brown, tan, and yellowish-brown with iron oxide staining; Luster: vitreous to dull/sugary; Structure: granular, interlocking quartz crystals; Cleavage: none.
Formation & geological history
Formed from quartz-rich sandstone subjected to high heat and pressure during regional metamorphism. Subsequently eroded and rounded by water transport in riverbed or glacial environments.
Uses & applications
Used widely in construction as decorative landscape rock, aggregate, dimension stone, and ballasts.
Geological facts
Quartzite is so tough that it fractures across the component quartz grains rather than along the grain boundaries, unlike sandstone.
Field identification & locations
Identified by its high hardness (scratches glass effortlessly), interlocking granular texture, and smooth, water-worn cobble shape. Found along riverbeds, beaches, and glacial deposits globally.
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