igneous
Vesicular basalt with secondary zeolite/mineral crusts
Basalt, chiefly plagioclase–pyroxene ± olivine; cavities partly filled by zeolites or calcite
AI-generated identification · may be incorrectDark gray to black, fine-grained volcanic rock with angular vesicles/fractures and brown-orange weathering or iron-oxide staining. Typically hardness 5–6, dull to weakly vitreous luster, no obvious cleavage, and specific gravity about 2.8–3.1.
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Physical properties
Dark gray to black, fine-grained volcanic rock with angular vesicles/fractures and brown-orange weathering or iron-oxide staining. Typically hardness 5–6, dull to weakly vitreous luster, no obvious cleavage, and specific gravity about 2.8–3.1.
Formation & geological history
Formed when basaltic lava cooled rapidly at or near the surface; gas bubbles produced the cavities, later becoming lined or filled by low-temperature minerals. The exact geological age cannot be determined from the photograph.
Uses & applications
Common basalt is used as aggregate, road stone, and building stone; attractive vesicular pieces are collected or cut as decorative material. This specimen appears more suitable for collecting than commercial use.
Geological facts
The pale, porous central zone may be altered basalt or zeolite-bearing amygdaloid rather than a separate sedimentary rock. Brown patches are likely iron oxides, though the image cannot confirm the cavity minerals.
Field identification & locations
Inspect broken cavities for radiating white zeolites, translucent calcite, or green epidote; a streak, hardness, and acid test would help distinguish them. Basalt is widespread in volcanic terrains, including Yemen’s Cenozoic volcanic fields near the reported location.
