metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White to tan/grey with sugary texture, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline/polycrystalline grains), Cleavage: None (conchoidal fracture), Specific Gravity: 2.63-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: White to tan/grey with sugary texture, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline/polycrystalline grains), Cleavage: None (conchoidal fracture), Specific Gravity: 2.63-2.65
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. This specific rounded shape was created by fluvial or glacial erosion (water or ice tumbling) over thousands of years.
Uses & applications
Used in construction as road ballast, railway ballast, and in the production of glass and silicon. Polished pebbles are used in landscaping and aquariums.
Geological facts
Quartzite is so hard that it will scratch glass. It is often more resistant than the surrounding rocks, which is why it commonly survives as rounded pebbles in riverbeds and on beaches long after other rocks have eroded.
Field identification & locations
Identify in the field by its inability to be scratched by a steel nail and its 'sugary' grain texture when viewed closely. Common in river beds and alluvial deposits globally.
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