metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, or off-white with iron staining; Luster: Dull to vitreous; Structure: Crystalline/Granular; Cleavage: None (conchoidal fracture). It is extremely durable and resistant to weathering.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, or off-white with iron staining
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, or off-white with iron staining; Luster: Dull to vitreous; Structure: Crystalline/Granular; Cleavage: None (conchoidal fracture). It is extremely durable and resistant to weathering.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure caused the original quartz grains to recrystallize and fuse together. The rounded shape indicates significant water erosion, likely in a riverbed or coastal environment.
Uses & applications
Used primarily as construction aggregate, railway ballast, and in road base. High-purity quartzite is used to produce glass and ferrosilicon. This specific rounded specimen is common in landscaping and decorative gravel.
Geological facts
Quartzite is so tough that it often breaks through the individual quartz grains rather than around them, unlike its parent rock sandstone. It is one of the most chemically and physically resistant rocks on Earth's surface.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary texture. Look for it in glaciated regions or river valleys where water has transported and rounded the material over thousands of years.
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