metamorphic
Tumbled quartzite pebble
Quartzite, predominantly crystalline SiO₂
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray to mauve-brown, with a smooth tumbled surface and vitreous to waxy luster. Massive, interlocking quartz grains; no obvious cleavage, and the yellow-brown seam is likely iron-oxide staining along a fracture.
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Physical properties
Hardness about 7 Mohs; pale gray to mauve-brown, with a smooth tumbled surface and vitreous to waxy luster. Massive, interlocking quartz grains; no obvious cleavage, and the yellow-brown seam is likely iron-oxide staining along a fracture.
Formation & geological history
Formed when quartz-rich sandstone was recrystallized under heat and pressure, commonly during regional mountain-building; its exact geological age cannot be determined from the image. Rounded shape indicates prolonged stream, beach, or deliberate tumbling abrasion.
Uses & applications
Used as durable aggregate, paving and building stone, landscaping material, and decorative polished stone; this ordinary pebble has little jewelry value.
Geological facts
Quartzite commonly resists weathering better than surrounding rocks, producing rounded resistant pebbles. A steel file should not scratch it, while quartzite can scratch ordinary glass.
Field identification & locations
Common in mountain-derived river gravels and glacial deposits worldwide; identify by its very high hardness, granular quartz texture, and lack of fizz with dilute acid. Exact identification would benefit from a fresh broken surface or microscope examination.
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