igneous
Likely basalt pebble
Basalt, a fine-grained mafic volcanic rock composed mainly of plagioclase feldspar and pyroxene, often with olivine
AI-generated identification · may be incorrectDark gray-green, dull, and fine-grained with scattered pits or small crystals; typical basalt hardness is about 6 on Mohs scale and its structure is too fine-grained to distinguish individual crystals easily. The image is dim, so identification is approximate.
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Physical properties
Dark gray-green, dull, and fine-grained with scattered pits or small crystals; typical basalt hardness is about 6 on Mohs scale and its structure is too fine-grained to distinguish individual crystals easily. The image is dim, so identification is approximate.
Formation & geological history
Forms when iron- and magnesium-rich lava cools quickly at or near Earth’s surface; basalt occurs from ancient volcanic terrains to recent lava flows.
Uses & applications
Used as crushed aggregate, road stone, and building material; attractive polished pieces may be collected or used decoratively.
Geological facts
Basalt is among Earth’s most abundant volcanic rocks and also forms much of the ocean floor.
Field identification & locations
Look for a dense, dark, fine-grained rock, sometimes with vesicles; common near volcanic regions and in river or beach gravel derived from them. A small ordinary pebble is typically worth about $0–$10; distinctive specimens may sell for more.
