metamorphic
Quartzite (River Pebble)
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-brown with lighter banding; Luster: Dull to vitreous; Structure: Granular/Crystalline; Cleavage: None (conchoidal fracture)
- Hardness
- 7 on Mohs scale
- Color
- Grayish-brown with lighter banding
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-brown with lighter banding; Luster: Dull to vitreous; Structure: Granular/Crystalline; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under heat and pressure. This specimen shows signs of fluvial erosion (river rounding).
Uses & applications
Commonly used in construction as crushed stone, railway ballast, or as decorative landscaping stones.
Geological facts
Quartzite is harder and more durable than the sandstone it originates from. It is so tough that it often outlasts other rocks in riverbeds, leading to the smooth pebble shapes seen here.
Field identification & locations
Identified by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in riverbeds, glacial deposits, and mountain ranges.
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