metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan, yellow, orange and pink tones, Luster: Vitreous to greasy when wet or polished, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, yellow, orange and pink tones, Luster: Vitreous to greasy when wet or polished, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, often in orogenic (mountain-building) belts. This specimen has been rounded by fluvial or coastal transport.
Uses & applications
Used in construction as a decorative aggregate, in the glass industry as a source of silica, and as a durable material for stone tools or landscaping.
Geological facts
Quartzite is so tough that it often outlasts other rocks in weathering processes; when it breaks, it breaks across the quartz grains rather than around them, unlike its parent rock, sandstone.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of visible grains compared to sandstone. Commonly found in riverbeds, glacial deposits, and along beaches globally.
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