igneous
Likely weathered basalt or iron-rich volcanic rock
Basalt; primarily plagioclase feldspar, pyroxene, and iron-rich oxides
AI-generated identification · may be incorrectDark reddish-brown, fine-grained, dull to slightly earthy luster, with possible vesicles and a dark mineral band; hardness about 5–6, no obvious cleavage, specific gravity roughly 2.8–3.1.
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Physical properties
Dark reddish-brown, fine-grained, dull to slightly earthy luster, with possible vesicles and a dark mineral band; hardness about 5–6, no obvious cleavage, specific gravity roughly 2.8–3.1.
Formation & geological history
An extrusive igneous rock formed when mafic lava cooled rapidly at or near Earth’s surface; its reddish coloration likely reflects oxidation and weathering of iron-bearing minerals. Exact geological age cannot be determined from the photograph.
Uses & applications
Common basalt is used as crushed aggregate, roadstone, railway ballast, building stone, and occasionally decorative material; ordinary hand specimens have little commercial value.
Geological facts
Basalt is the most abundant volcanic rock on Earth and forms much of the oceanic crust, as well as extensive lava plateaus and volcanic islands.
Field identification & locations
Identify it by its heavy, fine-grained dark body, lack of visible large crystals, and possible weak attraction to a magnet; a streak, hardness, density, and thin-section test would be needed for confirmation. Common worldwide, especially in volcanic regions.
