mineral
Likely dark rounded pebbles
Indeterminate; possibly basalt or a dark mafic mineral such as hornblende/biotite
AI-generated identification · may be incorrectSmall, wet, dark gray-green, rounded specimens with dull to weakly vitreous luster; hardness and crystal structure cannot be determined reliably from the image. They may be dense and fine-grained, with no visible cleavage or crystal faces.
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Physical properties
Small, wet, dark gray-green, rounded specimens with dull to weakly vitreous luster; hardness and crystal structure cannot be determined reliably from the image. They may be dense and fine-grained, with no visible cleavage or crystal faces.
Formation & geological history
If basalt, they formed as rapidly cooled volcanic lava, commonly in the Cenozoic or older; if individual minerals, they crystallized within igneous or metamorphic rocks. Their rounded shape likely reflects water or abrasion.
Uses & applications
Common basalt pebbles have landscaping, aggregate, and educational uses; attractive specimens may be collected but are generally low-value.
Geological facts
The image is insufficient for confident species identification because the specimens are tiny, wet, and lack visible diagnostic features.
Field identification & locations
Test streak, hardness, magnetism, density, and inspect a dry broken surface; basalt is typically fine-grained and may be weakly magnetic. Common sources include stream gravels, volcanic regions, and commercial landscaping materials.
