igneous
Black beach pebble (likely basalt)
Basalt, a fine-grained volcanic rock composed mainly of plagioclase and pyroxene, commonly with olivine
AI-generated identification · may be incorrectSmooth, rounded, dark gray to black pebble with a matte-to-slightly-waxy surface; basalt is typically Mohs 5–6, fine-grained, and lacks visible cleavage. The photo does not reveal its internal texture, so identification is provisional.
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Physical properties
Smooth, rounded, dark gray to black pebble with a matte-to-slightly-waxy surface; basalt is typically Mohs 5–6, fine-grained, and lacks visible cleavage. The photo does not reveal its internal texture, so identification is provisional.
Formation & geological history
Likely formed when basaltic lava cooled rapidly, then was rounded by water or abrasion; basalt ranges from recent to billions of years old.
Uses & applications
Commonly used as aggregate, paving stone, and landscaping material; smooth pebbles are also used in crafts and decoration.
Geological facts
Basalt is the most widespread volcanic rock in Earth’s oceanic crust.
Field identification & locations
A dark, dense pebble with fine or invisible grains and no obvious layering supports basalt; examine a fresh break to distinguish it from other dark stones. Rounded black pebbles occur on beaches and riverbeds worldwide.
