metamorphic
Quartzite Pebble (River-worn)
Metaquartzite (predominantly SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: mottled grayish-green to tan with subtle reddish/pinkish flecks; Luster: dull to vitreous where quartz grains glint; Texture: granoblastic, sugary granular appearance with rounded river-tumbled exterior; Specific gravity: ~2.65.
- Hardness
- 7 on Mohs scale
- Luster
- dull to vitreous where quartz grains glint
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Physical properties
Hardness: 7 on Mohs scale; Color: mottled grayish-green to tan with subtle reddish/pinkish flecks; Luster: dull to vitreous where quartz grains glint; Texture: granoblastic, sugary granular appearance with rounded river-tumbled exterior; Specific gravity: ~2.65.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone subjected to high temperatures and pressures, causing the original quartz grains to recrystallize into an interlocking mosaic. This specific rounded pebble shape is the result of mechanical weathering and transport in rivers or glacial waters.
Uses & applications
Quartzite is used extensively in crushed stone aggregate, railway ballast, dimension stone, and construction. In landscaping, river-worn quartzite pebbles are popular for decorative gardens and pathways.
Geological facts
Quartzite is so thoroughly recrystallized that unlike its parent rock sandstone, it fractures directly through the quartz grains rather than around them, making it one of the toughest and most erosion-resistant rocks on Earth.
Field identification & locations
Easily recognized by its ability to scratch glass or steel (Mohs 7), its interlocking sugary texture, and lack of reaction to dilute acid. Extremely abundant in riverbeds, glacial moraines, and gravel deposits worldwide.
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