metamorphic
Quartzite Pebble
Quartzite (primarily Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: Cream, tan, or white; Luster: Vitreous to waxy; Structure: Granular/Crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.7.
- Hardness
- 7 on Mohs scale
- Color
- Cream, tan, or white
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Cream, tan, or white; Luster: Vitreous to waxy; Structure: Granular/Crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped into a smooth pebble by fluvial (river) or coastal water erosion over thousands of years.
Uses & applications
Commonly used in construction as crushed stone or road ballast. High-purity quartzite is used to produce silica sand for glassmaking and industrial abrasives. Smooth pebbles are popular in landscaping and decorative masonry.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains because it resists weathering better than surrounding rocks. It is harder than a steel knife blade.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and lack of reaction to acid. Often found in riverbeds, glacial tills, and along beaches. For collectors, look for versions with unique colors or translucency.
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