metamorphic
Quartzite (River Pebble)
Quartzite (Mainly SiO2)
Hardness: 7 on Mohs scale; Color: Tan, yellowish-brown, or buff; Luster: Dull to waxy; Structure: Granular/Massive; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, yellowish-brown, or buff
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, yellowish-brown, or buff; Luster: Dull to waxy; Structure: Granular/Massive; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. This specific specimen has been further shaped and smoothed by fluvial (river) erosion over thousands of years.
Uses & applications
Used as aggregate in construction, road ballast, decorative landscaping stone, and occasionally in glassmaking if purity is high.
Geological facts
Quartzite is so hard that it will scratch glass and steel. In the Stone Age, it was sometimes used as a substitute for flint to create tools, though its lack of predictable cleavage made it harder to flake.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its granular, sugary texture on a fresh break. Commonly found in riverbeds, glacial tills, and ancient mountain ranges worldwide.
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