metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Grayish-white with pinkish-orange iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-white with pinkish-orange iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-white with pinkish-orange iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize and fuse together, creating a hard, interlocking mosaic of quartz crystals.
Uses & applications
Used as a ballast in railway construction, as an aggregate in road building, for architectural stone, and occasionally as a tumbling stone for hobbyists.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it was part of, appearing as rounded river pebbles or coastal cobbles long after other rocks have eroded away.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and its granular, sugary texture often visible in sunlight. Commonly found in riverbeds, glacial tills, and mountainous metamorphic terrains.
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