igneous
Vesicular basalt (scoria-like basalt fragment)
Basalt; primarily plagioclase, pyroxene, and commonly olivine, with small vesicles
AI-generated identification · may be incorrectDark gray-black, fine-grained, porous, and dull to slightly glassy; hardness about 5–6 Mohs, no visible cleavage, and typically ~2.7–3.0 specific gravity. The surface appears rough and vesicular, consistent with scoria or weathered basalt.
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Physical properties
Dark gray-black, fine-grained, porous, and dull to slightly glassy; hardness about 5–6 Mohs, no visible cleavage, and typically ~2.7–3.0 specific gravity. The surface appears rough and vesicular, consistent with scoria or weathered basalt.
Formation & geological history
Forms when mafic lava cools rapidly at or near Earth’s surface, trapping gas bubbles; specimens may range from recent volcanic material to ancient flows. Common in volcanic regions and basaltic lava fields.
Uses & applications
Used as aggregate, road base, landscaping stone, concrete additive, and lightweight construction material; attractive pieces may be collected, but this fragment has little gem value.
Geological facts
Basalt is the most abundant volcanic rock on oceanic crust and commonly forms pillow lavas underwater. Vesicles indicate gas-rich lava, while abundant interconnected holes would favor scoria over dense basalt.
Field identification & locations
Identify it by its black color, fine texture, magnetic response in some specimens, and porous surface; distinguish it from charcoal by its mineral hardness and lack of streaky organic texture. Common worldwide in volcanic terrains, including Hawaii, Iceland, the western United States, and oceanic islands.
