metamorphic
Quartzite River Pebble
Quartzite (primarily Silicon Dioxide, SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, and white; Luster: Vitreous to dull; Crystal Structure: Granular/Massive (no visible crystals); Cleavage: None/Conchoidal fracture.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, and white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, and white; Luster: Vitreous to dull; Crystal Structure: Granular/Massive (no visible crystals); Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed from quartz-rich sandstone subjected to high tectonic pressure and temperature (metamorphism), causing quartz grains to recrystallize. This specific specimen has been further shaped by fluvial erosion in a river or coastal environment, creating its rounded 'pebble' shape.
Uses & applications
Used primarily in landscaping, construction aggregate, and as a decorative stone in aquariums or zen gardens. High-purity quartzite is sometimes used as a source of silica for glass manufacturing.
Geological facts
Quartzite is so durable that it can survive long-term erosion better than almost any other rock. While it starts as sand, the resulting metamorphic rock is harder than the steel of a pocket knife.
Field identification & locations
Identify in the field by its hardness (it should scratch glass) and its sugary, granular appearance on unpolished surfaces. Common in riverbeds and mountainous glacial tills throughout North America and Europe.
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