metamorphic
Quartzite Pebbles
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: white, grey, or tan; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- white, grey, or tan
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white, grey, or tan; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. These specimens show significant rounding from alluvial or fluvial water erosion.
Uses & applications
Construction aggregate, glass manufacturing, decorative landscaping, and occasionally as a source of silica for industrial processes.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries, unlike the sandstone from which it originated.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary texture. Common in riverbeds and glacial deposits. Found globally in mountainous regions.
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