igneous or sedimentary
Basalt or Siltstone Pebbles
Mafic volcanic rock (Basalt) or Indurated Siltstone
Hardness: 5-7 (Mohs), Color: Dark grey to reddish-brown, Luster: Dull or earthy, Texture: Fine-grained to aphanitic, Shape: Well-rounded from water erosion.
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Physical properties
Hardness: 5-7 (Mohs), Color: Dark grey to reddish-brown, Luster: Dull or earthy, Texture: Fine-grained to aphanitic, Shape: Well-rounded from water erosion.
Formation & geological history
These are likely water-worn pebbles formed through historical volcanic activity or sedimentary deposition, then weathered and rounded by river or coastal action over millions of years.
Uses & applications
Commonly used as construction aggregate, landscaping stones, or decorative fill in gardens and aquariums.
Geological facts
Small rounded stones like these are often called river rocks or shingles; their smoothness is a direct result of mechanical weathering by moving water transporting them over long distances.
Field identification & locations
Identify in the field by their smooth, rounded edges and uniform fine-grained texture. They are ubiquitous in riverbeds, glacial tills, and along coastlines globally.
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