igneous
Rounded reddish basalt pebble
Basalt, a fine-grained mafic volcanic rock; likely iron-oxide stained
AI-generated identification · may be incorrectHardness about 6 Mohs; dark reddish-brown, matte to slightly dull luster, very fine-grained with no visible crystals or cleavage. The rounded shape indicates natural abrasion or tumbling, and tiny pits may reflect vesicles.
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Physical properties
Hardness about 6 Mohs; dark reddish-brown, matte to slightly dull luster, very fine-grained with no visible crystals or cleavage. The rounded shape indicates natural abrasion or tumbling, and tiny pits may reflect vesicles.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava rapidly cools at or near Earth’s surface, commonly in volcanic flows; its age cannot be determined from the photograph. The pebble was likely shaped by stream, beach, or glacial transport.
Uses & applications
Used as aggregate, road stone, riprap, and occasionally decorative landscaping material; this small specimen has modest display value.
Geological facts
Its red-brown color commonly results from oxidation of iron-bearing minerals such as pyroxene and magnetite. The orange patch may be localized iron-oxide staining or weathering.
Field identification & locations
Identify it by its substantial weight, fine texture, dark mafic color, lack of layering, and inability to scratch easily with a steel knife; a streak, acid, and magnet test can help distinguish basalt from other dark pebbles. Common worldwide in volcanic and river environments.
