igneous
Weathered volcanic rock, likely altered basalt
Basaltic rock, probably chlorite–epidote–iron-oxide altered basalt
AI-generated identification · may be incorrectFine-grained, dull earthy luster, pale green-gray to brown-red from weathering and iron oxides; likely Mohs hardness 5–6, with no visible cleavage or large crystals. The irregular, vesicle-poor texture is consistent with a weathered mafic volcanic rock.
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Physical properties
Fine-grained, dull earthy luster, pale green-gray to brown-red from weathering and iron oxides; likely Mohs hardness 5–6, with no visible cleavage or large crystals. The irregular, vesicle-poor texture is consistent with a weathered mafic volcanic rock.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface, commonly in oceanic crust, lava flows, and volcanic islands; alteration may occur through circulating hydrothermal fluids over millions to billions of years. Exact age and identity require a fresh surface, hardness testing, and ideally thin-section or chemical analysis.
Uses & applications
Ordinary basalt is used as crushed aggregate, roadstone, riprap, and building stone; attractive pieces may be collected, but this specimen appears common and unpolished.
Geological facts
Green coloration can reflect chlorite, epidote, or other secondary minerals, while reddish patches usually indicate oxidized iron. It is not possible to confirm a specific mineral assemblage from the photograph alone.
Field identification & locations
Look for a dense dark-gray fresh interior, fine grain, weak magnetism, and hardness sufficient to scratch glass; vesicles or tiny feldspar crystals may occur. Common sources include volcanic regions worldwide, especially oceanic islands and basalt plateaus.
