igneous
Weathered volcanic rock, probably basaltic scoria or vesicular basalt
Vesicular basalt; predominantly plagioclase, clinopyroxene, olivine, and volcanic glass/iron oxides
AI-generated identification · may be incorrectDark gray-brown, fine-grained and porous with rusty iron-oxide staining; dull to slightly earthy luster and no visible cleavage. Hardness about 5–6 Mohs; typically dense but locally vesicular, with specific gravity roughly 2.4–3.0.
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Physical properties
Dark gray-brown, fine-grained and porous with rusty iron-oxide staining; dull to slightly earthy luster and no visible cleavage. Hardness about 5–6 Mohs; typically dense but locally vesicular, with specific gravity roughly 2.4–3.0.
Formation & geological history
An extrusive igneous rock formed when basaltic lava cooled rapidly at or near the surface, trapping gas bubbles; likely Quaternary to older volcanic age, depending on locality. Weathering oxidized iron-bearing minerals to brown-orange patches.
Uses & applications
Used as aggregate, road base, riprap, landscaping stone, and occasionally as lightweight scoria; this small weathered piece has little gem or collector value.
Geological facts
Basalt is the most common volcanic rock on Earth and forms much of the oceanic crust. Vesicles indicate gas escape during eruption, while scoria is generally more strongly vesicular and lightweight than this specimen.
Field identification & locations
Identify it by its dark fine-grained matrix, irregular pores, and strong resistance to scratching with a steel knife; it should not fizz with dilute acid. Common in volcanic regions, lava fields, and basalt cobbles.
