metamorphic
Quartzite River Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, brown, and grey with iron staining; Luster: Dull to waxy when unpolished; Structure: Granular/Massive; Cleavage: None; SG: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brown, and grey with iron staining
- Luster
- Dull to waxy when unpolished
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brown, and grey with iron staining; Luster: Dull to waxy when unpolished; Structure: Granular/Massive; Cleavage: None; SG: 2.6-2.7
Formation & geological history
Formed from quartz-rich sandstone subjected to extreme heat and pressure (metamorphism). This specimen likely originated as a larger mass that was eroded and water-worn in a river or glacial deposit over millions of years.
Uses & applications
Common river stones are used in landscaping, construction aggregate, and as tumbling media for hobbyist rock collectors.
Geological facts
Quartzite is so strong that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike sandstone.
Field identification & locations
Identify by its hardness (it will scratch glass) and its rounded, water-worn shape. Commonly found in riverbeds, beaches, and glacial till globally.
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