metamorphic
Quartzite Pebble
Metamorphic Quartzite
Hardness: 7 on Mohs scale, Color: Light gray to brownish-gray, Luster: Vitreous to sub-vitreous on fresh breaks, Crystal structure: Interlocking quartz crystals (non-foliated), Cleavage: None, Specific Gravity: 2.65
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Physical properties
Hardness: 7 on Mohs scale, Color: Light gray to brownish-gray, Luster: Vitreous to sub-vitreous on fresh breaks, Crystal structure: Interlocking quartz crystals (non-foliated), Cleavage: None, Specific Gravity: 2.65
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to heat and pressure through regional metamorphism.
Uses & applications
Used in construction, railroad ballast, crushed stone for road surfaces, and occasionally decorative landscaping.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz sandstone parent rocks often survive as resistant ridges or water-worn pebbles in stream beds long after other rocks have eroded.
Field identification & locations
Can be identified by its glassy sheen on broken surfaces, extreme hardness that easily scratches glass, and lack of reaction to hydrochloric acid. Commonly found in riverbeds, glacial tills, and ancient beach deposits.
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