metamorphic
Polished gray pebble, likely quartzite or fine-grained granite
Probable quartzite (mostly microcrystalline SiO₂); identification is uncertain from the photograph
AI-generated identification · may be incorrectGray-brown, smoothly tumbled surface with subdued vitreous-to-waxy luster and faint granular texture. Likely hardness 6.5–7 Mohs, no obvious cleavage, and moderate-to-high specific gravity around 2.6–2.7.
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Physical properties
Gray-brown, smoothly tumbled surface with subdued vitreous-to-waxy luster and faint granular texture. Likely hardness 6.5–7 Mohs, no obvious cleavage, and moderate-to-high specific gravity around 2.6–2.7.
Formation & geological history
If quartzite, it formed when quartz-rich sandstone was metamorphosed under heat and pressure, commonly during Precambrian to Phanerozoic mountain-building events. Its rounded shape is human-tumbled or naturally water-worn.
Uses & applications
Used as a decorative pebble, paperweight, landscaping stone, or craft material; not generally valuable for jewelry unless unusually patterned or translucent.
Geological facts
The specimen’s smooth finish and lack of visible crystals make precise identification difficult; it could also be a weathered quartz-rich igneous rock or chert.
Field identification & locations
Scratch testing with a steel file or glass can help: quartzite should scratch glass and resist steel. Common sources include river gravels, glacial deposits, and commercial tumbling batches worldwide.
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