metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Brownish-grey to tan, translucent in thin edges. Luster: Waxy to vitreous. Crystal Structure: Hexagonal (microcrystalline aggregate). Cleavage: None, conchoidal to uneven fracture. Specific gravity: ~2.65.
- Hardness
- 7 on Mohs scale
- Color
- Brownish-grey to tan, translucent in thin edges
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale. Color: Brownish-grey to tan, translucent in thin edges. Luster: Waxy to vitreous. Crystal Structure: Hexagonal (microcrystalline aggregate). Cleavage: None, conchoidal to uneven fracture. Specific gravity: ~2.65.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under high heat and pressure, recrystallizing quartz grains into a dense, interlocking matrix. Subsequently eroded and rounded by stream or beach action.
Uses & applications
Commonly collected as river rocks or beach pebbles, used in rock tumbling, landscaping, construction aggregate, and lapidary practice.
Geological facts
Quartzite pebbles are extremely durable and resistant to chemical weathering. When struck, quartzite breaks across its quartz grains rather than along grain boundaries like sandstone.
Field identification & locations
Identified by its extreme hardness (scratches glass readily), smooth water-worn surface, waxy texture, and interlocking crystalline texture under magnification. Commonly found in gravel bars, riverbeds, and glacial till deposits.
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