metamorphic
Quartzite Pebble (River Rock)
Quartzite (primarily SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: light gray to off-white/beige; Luster: dull to slightly vitreous; Structure: granoblastic, interlocking quartz grains; Cleavage: none (conchoidal to uneven fracture); Specific Gravity: ~2.65.
- Hardness
- 7 on Mohs scale
- Color
- light gray to off-white/beige
- Luster
- dull to slightly vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: light gray to off-white/beige; Luster: dull to slightly vitreous; Structure: granoblastic, interlocking quartz grains; Cleavage: none (conchoidal to uneven fracture); Specific Gravity: ~2.65.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under intense heat and pressure, causing quartz grains to recrystallize into a dense network. Subsequently smoothed and rounded by river or coastal mechanical erosion over thousands to millions of years.
Uses & applications
Commonly used as decorative landscape stone, garden mulch, in water features, path gravel, and historically as durable ballast or construction aggregate.
Geological facts
Quartzite is so tough that when it breaks, it fractures through the individual quartz grains rather than along the boundaries between them, unlike its parent rock, sandstone.
Field identification & locations
Identified by its high hardness (scratches glass and steel easily), sugary to crystalline surface texture when inspected closely, and smooth rounded pebble morphology. Abundant in riverbeds, glacial deposits, and gravel beaches worldwide.
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