igneous
Vesicular basalt (possibly weathered scoria)
Basalt; chiefly plagioclase feldspar, pyroxene, and iron-rich minerals
AI-generated identification · may be incorrectDark gray-green, fine-grained, dull to weakly silky, with abundant irregular vesicles and weathering pits; typically hardness 5–6, no visible cleavage, and specific gravity about 2.7–3.1. The pale pink material may be an alteration or secondary mineral filling a cavity, such as zeolite or calcite.
Identified More igneous →
Explore Vesicular basalt (possibly weathered scoria) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-green, fine-grained, dull to weakly silky, with abundant irregular vesicles and weathering pits; typically hardness 5–6, no visible cleavage, and specific gravity about 2.7–3.1. The pale pink material may be an alteration or secondary mineral filling a cavity, such as zeolite or calcite.
Formation & geological history
An extrusive igneous rock formed when basaltic lava cooled rapidly at or near Earth’s surface, trapping gas bubbles; commonly Cenozoic to recent, though basalt occurs throughout geologic time. Surface weathering has rounded and oxidized the specimen.
Uses & applications
Used as crushed aggregate, road stone, riprap, and occasionally lightweight construction material; attractive vesicular pieces are collected or used in landscaping. This specimen has little gem value.
Geological facts
Vesicles distinguish it from dense basalt, while scoria is generally more strongly vesicular and commonly reddish from oxidation. The cavity filling could be tested with a steel nail, streak, and dilute acid if calcite is suspected.
Field identification & locations
Common in volcanic regions, oceanic islands, mid-ocean ridges, and continental lava fields; notable sources include Hawaii, Iceland, Oregon, India, and Japan. Identify by its dark fine-grained matrix, low-density holes, and lack of large crystals.
