igneous
Small dark rock fragment
Indeterminate; possibly basalt or scoria
AI-generated identification · may be incorrectDark gray to black, irregular and angular, with a dull to slightly glassy luster; apparent grain and porosity are obscured by the low-resolution image. Likely hardness about 5–6 Mohs if basaltic, but cleavage, crystal structure, and density cannot be reliably determined visually.
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Physical properties
Dark gray to black, irregular and angular, with a dull to slightly glassy luster; apparent grain and porosity are obscured by the low-resolution image. Likely hardness about 5–6 Mohs if basaltic, but cleavage, crystal structure, and density cannot be reliably determined visually.
Formation & geological history
If basalt, it formed when mafic lava cooled rapidly at or near Earth’s surface, commonly during the Cenozoic or older volcanic episodes; if scoria, trapped gas produced its vesicles. Exact identification and age require a close-up, fresh surface, and tests.
Uses & applications
Ordinary fragments have little industrial or jewelry use; basalt is widely used as aggregate, roadstone, riprap, and building stone. Attractive polished pieces may be sold as curiosities.
Geological facts
The specimen’s silhouette is consistent with a weathered volcanic fragment, but it could also be slag or another dark rock; scale and lighting are insufficient for certainty.
Field identification & locations
Check for visible holes, a fine-grained matrix, and tiny white plagioclase crystals; test streak, magnetism, hardness, and specific gravity, and inspect a broken face. Common basalt sources include volcanic regions worldwide.
