metamorphic
Quartzite Pebble
Metamorphic Quartzite (SiO2)
Hardness: 7 on the Mohs scale; Color: Tan to off-white with yellowish hues; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None (fractures conchoidally); Specific gravity: 2.65
- Hardness
- 7 on the Mohs scale
- Color
- Tan to off-white with yellowish hues
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale; Color: Tan to off-white with yellowish hues; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None (fractures conchoidally); Specific gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high heat and tectonic pressure, typically during ancient mountain-building events over millions of years.
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 as rounded pebbles in riverbeds and beaches long after other minerals have eroded away.
Field identification & locations
Can be identified in the field by its high hardness (it will easily scratch glass and cannot be scratched by a knife), lack of cleavage, and sugary texture on freshly broken surfaces. Commonly found in river gravels, glacial tills, and ancient sedimentary formations worldwide.
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