igneous
Rounded gray-green pebble, likely basaltic or metamorphic
Indeterminate mafic rock; possibly basalt, diabase, or greenstone
AI-generated identification · may be incorrectFine-grained, dull to subtly satin luster, gray-green color, and rounded waterworn form; estimated hardness 5–6 Mohs, with no visible cleavage or crystals. The pale lines may be veins, fractures, or surface markings.
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Physical properties
Fine-grained, dull to subtly satin luster, gray-green color, and rounded waterworn form; estimated hardness 5–6 Mohs, with no visible cleavage or crystals. The pale lines may be veins, fractures, or surface markings.
Formation & geological history
Probably formed as a volcanic mafic rock or low-grade metamorphic greenstone, then weathered and rounded by stream or shoreline transport. Its geological age cannot be determined from the photograph.
Uses & applications
Commonly a landscape, teaching, or collection specimen; unexceptional pieces have little industrial or jewelry value, though crushed basalt is used for aggregate.
Geological facts
Basaltic rocks commonly contain plagioclase and pyroxene, with alteration minerals such as chlorite producing green hues. A photograph cannot reliably distinguish basalt from similar dark metamorphic rocks.
Field identification & locations
Inspect a fresh broken surface for fine grains, dark minerals, and possible tiny feldspar crystals; a streak, hardness, density, and acid test would help. Common worldwide in volcanic regions, river gravels, and beaches.
