metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Grayish-white to tan; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-white to tan
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-white to tan; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together, often in ancient mountain-building events.
Uses & applications
Larger deposits are used for railway ballast, construction aggregate, and manufacturing glass. Smooth pebbles are popular for landscaping and decorative accents.
Geological facts
Quartzite is so tough that it often survives erosion better than other rocks, frequently appearing as rounded river stones or capping high mountain ridges. It usually breaks across the grains rather than around them.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary surface texture. Commonly found in riverbeds, glacial tills, and mountainous metamorphic terrains.
