metamorphic
Quartzite Pebbles (River Stones)
Quartzite (primarily Silicon Dioxide, SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, gray, and white with iron staining; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, gray, and white with iron staining
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, gray, and white with iron staining; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. These specific specimens have been smoothed and rounded by long-term fluvial (river) erosion.
Uses & applications
Commonly used in landscaping (river rock), construction aggregate, and as decorative garden stones. High-purity quartzite is used as a source of silica for glass making.
Geological facts
Quartzite is so hard that it can scratch glass and steel. Most river pebbles like these have traveled miles from their original source, becoming naturally polished by the action of water and abrasive sand.
Field identification & locations
Identify in the field by their extreme hardness, rounded 'cobble' shape, and lack of visible grains. They are commonly found in riverbeds, glacial deposits, and coastal beaches.
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