igneous
Dark gray-green pebble, likely basalt
Fine-grained basalt (tentative; image alone cannot confirm composition)
AI-generated identification · may be incorrectSmooth, rounded, fine-grained surface; dark gray-green with small pale specks and a subdued luster. Basalt is typically Mohs 5–6, composed mainly of plagioclase and pyroxene, sometimes olivine; crystals are too small to see clearly.
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Physical properties
Smooth, rounded, fine-grained surface; dark gray-green with small pale specks and a subdued luster. Basalt is typically Mohs 5–6, composed mainly of plagioclase and pyroxene, sometimes olivine; crystals are too small to see clearly.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface. Its age and exact origin cannot be determined from the photograph.
Uses & applications
Commonly used as crushed aggregate, road stone, and building material; a pebble of this size is mainly suitable for collecting or decoration.
Geological facts
Water-worn surfaces can make basalt look unusually smooth and obscure its original texture.
Field identification & locations
The rounded shape suggests transport by water or surf. Check for a dense, fine-grained interior and use a streak or hardness test; similar-looking stones may be other volcanic rocks.
