metamorphic
Quartzite River Rock
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
- Hardness
- 7 on Mohs scale
- Color
- White to light grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under high heat and pressure, typically in orogenic belts. This specific specimen has been further shaped and smoothed by fluvial (river) erosion.
Uses & applications
Used in construction as crushed stone, railway ballast, and decorative landscaping. High-purity quartzite is used to produce glass and industrial silica.
Geological facts
Quartzite is so durable that it often outlasts the surrounding rocks during erosion, remaining as resistant ridges or rounded river cobbles like this one. It is harder than a steel knife and will scratch glass.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and its granular, sugary texture. It is commonly found in riverbeds, glacial tills, and mountainous regions worldwide.
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