metamorphic
Quartzite Pebble
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Tan, brown, or light orange due to iron oxide staining; Luster: Vitreous to waxy when wet; Crystal structure: Non-foliated granoblastic; Cleavage: None, breaks with conchoidal fracture.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brown, or light orange due to iron oxide staining
- Luster
- Vitreous to waxy when wet
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brown, or light orange due to iron oxide staining; Luster: Vitreous to waxy when wet; Crystal structure: Non-foliated granoblastic; Cleavage: None, breaks with conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Extreme heat and pressure cause quartz grains to recrystallize and fuse together. This specific specimen has been rounded by fluvial (river) or glacial erosion.
Uses & applications
Commonly used as decorative garden stone, railway ballast, and in the manufacturing of glass and ceramics when pure. Small pebbles like this are often collected for rock tumbling.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, creating high ridges or staying preserved as rounded pebbles in riverbeds for millions of years.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sugary texture under the surface. It is very common in riverbeds and glacial tilling areas across North America and Europe.
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