igneous
Weathered iron-rich volcanic rock
Likely basaltic andesite or altered basalt; precise identification requires testing
AI-generated identification · may be incorrectDark gray to brown, fine-grained and strongly weathered, with rusty yellow-brown iron-oxide staining and scattered dark grains or vesicles. Estimated hardness 5–6, dull to earthy luster, no obvious cleavage, and likely specific gravity about 2.7–3.0.
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Physical properties
Dark gray to brown, fine-grained and strongly weathered, with rusty yellow-brown iron-oxide staining and scattered dark grains or vesicles. Estimated hardness 5–6, dull to earthy luster, no obvious cleavage, and likely specific gravity about 2.7–3.0.
Formation & geological history
Probably formed from rapidly cooled lava in a volcanic environment, then chemically weathered and oxidized near the surface. Its exact geological age cannot be determined from the image.
Uses & applications
Common basaltic rocks are used as crushed aggregate, road stone, riprap, and occasionally building stone; this weathered specimen has little commercial value.
Geological facts
The ochre coloration commonly reflects limonite/goethite produced when iron-bearing minerals alter. A fresh broken surface would be more diagnostic than the weathered exterior.
Field identification & locations
Look for a dense, fine-grained texture, weak magnetism, and a dark fresh interior; a streak, hardness, acid, and thin-section test can distinguish basalt from andesite or ore-bearing rock. Volcanic equivalents occur worldwide.
