metamorphic
Quartzite (River Pebble)
Quartzite
Hardness: 7 on Mohs scale. Color: Grayish-blue with yellowish-tan iron oxide weathering. Luster: Vitreous to dull. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None (conchoidal to uneven fracture). Specific gravity: ~2.65.
- Hardness
- 7 on Mohs scale
- Color
- Grayish-blue with yellowish-tan iron oxide weathering
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Grayish-blue with yellowish-tan iron oxide weathering. Luster: Vitreous to dull. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None (conchoidal to uneven fracture). Specific gravity: ~2.65.
Formation & geological history
Formed from the regional or contact metamorphism of quartz-rich sandstone under intense heat and pressure, recrystallizing the quartz grains into a interlocking network. Later eroded and rounded by water action into a river pebble.
Uses & applications
Commonly used as construction aggregate, railway ballast, landscaping gravel, and decorative stone. Smooth pebbles are also collected casually.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering. It is often much harder and more resistant than the surrounding rocks, allowing it to survive long-distance transport in rivers and streams.
Field identification & locations
Identified by its high hardness (scratches glass easily) and granular, sugary texture fused together. Commonly found in riverbeds, glacial deposits, beaches, and mountainous regions worldwide.
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