metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: ~7 on Mohs scale. Color: Pale yellowish-grey to beige with iron staining. Luster: Dull to vitreous/sugary. Structure: Granoblastic interlocking quartz grains. Cleavage: None. Specific Gravity: ~2.65.
- Hardness
- ~7 on Mohs scale
- Color
- Pale yellowish-grey to beige with iron staining
- Luster
- Dull to vitreous/sugary
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Physical properties
Hardness: ~7 on Mohs scale. Color: Pale yellowish-grey to beige with iron staining. Luster: Dull to vitreous/sugary. Structure: Granoblastic interlocking quartz grains. Cleavage: None. Specific Gravity: ~2.65.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under intense heat and pressure, causing quartz grains to recrystallize into an interlocking network. Later weathered and rounded by water action in a stream, river, or coastal environment.
Uses & applications
Used primarily as aggregate in construction, railway ballast, landscape stone, and occasionally for minor decorative pebble craft.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering. When struck with a hammer, it fractures across quartz grains rather than along grain boundaries like its parent sandstone.
Field identification & locations
Look for a sugary surface texture with rounded, water-worn edges. It cannot be easily scratched by a steel pocket knife or nail due to its high quartz content. Very common in riverbeds, glacial deposits, and coastal beaches worldwide.
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