metamorphic
Quartzite pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Brownish-grey with white veins; Luster: Dull to vitreous; Structure: Granoblastic/Non-foliated; Cleavage: None
- Hardness
- 7 (Mohs scale)
- Color
- Brownish-grey with white veins
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Brownish-grey with white veins; Luster: Dull to vitreous; Structure: Granoblastic/Non-foliated; Cleavage: None
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under high heat and pressure, causing quartz grains to recrystallize and fuse together. Likely water-worn into a pebble shape.
Uses & applications
Commonly used as crushed stone in road construction, as railroad ballast, and for architectural facing or decorative garden stones.
Geological facts
Quartzite is so tough that it often survives intense weathering and erosion better than the surrounding rocks, which is why it is frequently found as rounded pebbles in stream beds.
Field identification & locations
Identify by its high hardness (it will scratch glass) and lack of reaction to acid. Look for a sugary texture on fresh breaks. Found globally in mountainous regions.
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