metamorphic
Quartzite Pebble
Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 on the Mohs scale; Color: grayish-white with mottled reddish-brown streaks; Luster: dull to vitreous; Grain structure: granular, non-foliated, fused quartz grains.
- Hardness
- 7 on the Mohs scale
- Color
- grayish-white with mottled reddish-brown streaks
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 on the Mohs scale; Color: grayish-white with mottled reddish-brown streaks; Luster: dull to vitreous; Grain structure: granular, non-foliated, fused quartz grains.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone, where intense heat and pressure recrystallize quartz grains into a dense, interlocking matrix. Highly resistant to physical weathering, leading to rounded pebbles in riverbeds and beach gravels.
Uses & applications
Used as aggregate in construction, railway ballast, decorative landscaping, and occasionally as raw material for silica extraction in glass and metallurgy.
Geological facts
Quartzite is so tough that when it breaks, the fractures cut directly through the individual quartz grains rather than along the boundaries between them, unlike sandstone.
Field identification & locations
Identified by its high hardness (scratches glass easily) and granular sugary surface texture. Commonly found in stream beds, glacial till, and coastal gravel deposits worldwide.
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