metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on the Mohs scale; Color: Shades of brown, tan, gray, or white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None, breaks with a conchoidal fracture; Specific Gravity: 2.65
- Hardness
- 7 on the Mohs scale
- Color
- Shades of brown, tan, gray, or white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on the Mohs scale; Color: Shades of brown, tan, gray, or white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None, breaks with a conchoidal fracture; Specific Gravity: 2.65
Formation & geological history
Formed from quartz-rich sandstone subjected to high heat and tectonic pressure during regional metamorphism, typically taking millions of years in mountain-building or deep crustal environments.
Uses & applications
Used in landscaping, decorative gravel, road construction, and occasionally in architecture due to its high durability and weather resistance.
Geological facts
Quartzite is extremely resistant to chemical weathering and erosion, which is why quartz-rich rocks often survive as smooth, rounded pebbles in riverbeds and beaches long after other minerals have weathered away.
Field identification & locations
Found worldwide in stream beds, glacial tills, and ancient sedimentary basins. It can be identified by its inability to be scratched by a steel knife and its tough, interlocking grain texture visible under a hand lens.
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