metamorphic
Quartzite (River Pebble)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, yellowish-brown, and white; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.63-2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, yellowish-brown, and white
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, yellowish-brown, and white; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.63-2.65.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, followed by fluvial erosion (river action) which rounded the specimen over many years.
Uses & applications
Common varieties are used in construction, road ballast, and landscaping. Smooth specimens are popular for rock tumbling and decorative aquarium use.
Geological facts
Quartzite is so durable that it often survives long transport in rivers that would crush other rocks. It is harder than steel and will scratch glass easily.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel blade) and its granular, sugary texture on fresh breaks. Very common in riverbeds and glacial deposits throughout North America.
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