metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White to light grey (translucent); Luster: Dull to vitreous; Crystal Structure: Granular/Massive; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to light grey (translucent)
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light grey (translucent); Luster: Dull to vitreous; Crystal Structure: Granular/Massive; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the original sand grains to recrystallize and fuse together. These pebbles are typically smoothed and rounded by long-term water erosion in riverbeds or coastal environments.
Uses & applications
Used as a decorative stone in landscaping, as a construction aggregate, for railroad ballast, and occasionally in the production of glass or silica-based ceramics.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers during mountain-building processes, frequently forming the peaks of ridges. It is harder than steel, meaning it will easily scratch a knife blade.
Field identification & locations
Identify in the field by its extreme hardness, granular 'sparkly' appearance when broken, and lack of reaction to acid. It is found globally in areas with metamorphic basements or along beaches and rivers where secondary erosion has deposited them.
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