metamorphic
Quartz / Quartzite Pebble
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Off-white, white, or milky with tan iron staining; Luster: Vitreous to greasy; Structure: Hexagonal (though often massive/crystalline in pebbles); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Off-white, white, or milky with tan iron staining
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white, white, or milky with tan iron staining; Luster: Vitreous to greasy; Structure: Hexagonal (though often massive/crystalline in pebbles); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone (quartzite) or as hydrothermal vein deposits. This specific specimen has been chemically and mechanically weathered, likely tumbled by water in a river or coastal environment to its current rounded shape.
Uses & applications
In this rounded form, they are primarily used in landscaping, construction aggregate, and as 'river rocks' for decorative drainage. Crushed quartzite is used in glass making and abrasives.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. These rounded pebbles are often much older than the landscape they are found in, having resisted erosion that wore away softer surrounding minerals.
Field identification & locations
Identify in the field by its hardness (it will scratch glass and cannot be scratched by a steel knife) and its white/milky translucency. Commonly found in gravel pits, riverbeds, and glacial till worldwide.
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