igneous
Vesicular basalt (possibly scoriaceous basalt)
Basalt; predominantly plagioclase feldspar, clinopyroxene, and Fe-Ti oxides, with possible olivine
AI-generated identification · may be incorrectDark gray-black, fine-grained and locally vesicular, with dull to faintly glassy luster; hardness about 5–6, no obvious cleavage, and typical specific gravity around 2.8–3.1. The pale material may be weathered alteration, carbonate, or infilling mineral.
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Physical properties
Dark gray-black, fine-grained and locally vesicular, with dull to faintly glassy luster; hardness about 5–6, no obvious cleavage, and typical specific gravity around 2.8–3.1. The pale material may be weathered alteration, carbonate, or infilling mineral.
Formation & geological history
An extrusive mafic igneous rock formed when basaltic lava cooled rapidly at or near Earth’s surface; its exact geological age cannot be determined from the photograph. Vesicles formed from gas bubbles, later possibly filled by secondary minerals.
Uses & applications
Commonly used as crushed aggregate, roadstone, riprap, and occasionally decorative stone; attractive vesicular pieces are collected but rarely valuable.
Geological facts
Basalt is the most abundant volcanic rock in Earth’s oceanic crust and commonly forms lava flows, dikes, and volcanic islands.
Field identification & locations
Identify by its dark color, fine texture, high density, and vesicles; distinguish it from slag by its natural mineral texture and lack of uniformly glassy, metallic surfaces. Common worldwide, especially oceanic islands, volcanic plateaus, and mid-ocean-ridge settings.
