metamorphic
Quartzite River Rock
Metamorphosed Quartz-rich Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, grey, and orange-tinted due to iron oxides; Luster: Dull to vitreous; Crystal structure: Granular, interlocking quartz crystals; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, grey, and orange-tinted due to iron oxides
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, grey, and orange-tinted due to iron oxides; Luster: Dull to vitreous; Crystal structure: Granular, interlocking quartz crystals; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically in orogenic belts. This specific specimen has been rounded by fluvial (river) erosion over thousands of years.
Uses & applications
Used in landscaping, construction as crushed stone or ballast, and as a durable material for pathways or water features.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock during weathering, leading to the formation of ridges and peaks in mountainous terrain.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sandpaper-like texture that doesn't rub off. Common in riverbeds and glacial deposits worldwide.
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