metamorphic
Quartzite Pebble
Quartzite (Metamorphosed Quartz Sandstone, SiO2)
Hardness: 7 on the Mohs scale; Color: Tan, brown, reddish-brown, or light gray; Luster: Vitreous to greasy on fresh surfaces, matte when weathered; Crystal structure: Interlocking quartz grains (microcrystalline to crystalline); Cleavage: None, breaks with a conchoidal fracture; Specific Gravity: 2.65 - 2.75
- Hardness
- 7 on the Mohs scale
- Color
- Tan, brown, reddish-brown, or light gray
- Luster
- Vitreous to greasy on fresh surfaces, matte when weathered
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Physical properties
Hardness: 7 on the Mohs scale; Color: Tan, brown, reddish-brown, or light gray; Luster: Vitreous to greasy on fresh surfaces, matte when weathered; Crystal structure: Interlocking quartz grains (microcrystalline to crystalline); Cleavage: None, breaks with a conchoidal fracture; Specific Gravity: 2.65 - 2.75
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high tectonic heat and pressure, typically in mountain-building events over millions of years. This specific specimen has been smoothed and rounded into a pebble by wave action in a beach or river environment.
Uses & applications
Used in landscaping, decorative stone, construction aggregate, and occasionally as a tumbling or lapidary specimen.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich rocks often survive long journeys in riverbeds and shorelines long after other rock types have eroded away.
Field identification & locations
Can be identified in the field by its extreme hardness (will easily scratch glass and cannot be scratched by a steel knife) and the sugary texture of interlocking quartz grains visible on broken surfaces. Commonly found in riverbeds, glacial tills, and beaches worldwide.
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