metamorphic
Quartzite River Pebble
Quartzite (principally SiO2)
Hardness: 7 (Mohs scale); Color: Tan, brown, and translucent white; Luster: Vitreous to waxy when wet; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture).
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brown, and translucent white
- Luster
- Vitreous to waxy when wet
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brown, and translucent white; Luster: Vitreous to waxy when wet; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, followed by mechanical weathering and smoothing in a high-energy aquatic environment like a river or beach.
Uses & applications
Used as decorative gravel, in landscaping, as a construction aggregate, and occasionally tumbled by hobbyists for use in jewelry or collections.
Geological facts
Quartzite is so durable that it often outlasts the mountain ranges from which it originated. It is often confused with quartz, but its grainy, sugary texture under magnification distinguishes its sedimentary history.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel blade) and its rounded, water-worn shape. Commonly found in riverbeds, glacial deposits, and along coastlines.
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