igneous
Weathered basaltic river pebble
Basalt, likely with iron-oxide weathering and secondary alteration minerals
AI-generated identification · may be incorrectFine-grained, massive stone with muted green-gray and reddish-brown patches, earthy to dull luster, and no visible crystals or cleavage. Typical hardness is about 5–6 Mohs; density commonly 2.8–3.1 g/cm³.
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Physical properties
Fine-grained, massive stone with muted green-gray and reddish-brown patches, earthy to dull luster, and no visible crystals or cleavage. Typical hardness is about 5–6 Mohs; density commonly 2.8–3.1 g/cm³.
Formation & geological history
Basalt forms when low-silica lava cools rapidly at or near Earth’s surface; the rounded shape indicates prolonged stream or beach transport. Its surface colors likely result from oxidation and weathering of iron-bearing minerals, generally over geologically young exposure times.
Uses & applications
Commonly used as aggregate, riprap, paving stone, and landscaping material; attractive pieces may be collected or polished, but this specimen has limited jewelry value.
Geological facts
Basalt commonly contains plagioclase, pyroxene, and sometimes olivine or magnetite. Green coloration can reflect chlorite or other alteration minerals, while red-brown areas are typically iron oxides.
Field identification & locations
Identify it by its fine texture, heavy feel, dark mafic color, and lack of obvious layering or large crystals; a streak, magnetism test, and fresh chip would improve certainty. Common worldwide, especially in volcanic regions and river gravels.
