igneous
Vesicular basalt (possibly scoriaceous basalt)
Basalt, primarily plagioclase + clinopyroxene ± olivine; vesicles may be lined with secondary zeolites or calcite
AI-generated identification · may be incorrectDark gray to brown/purplish, highly porous, and typically dull to slightly vitreous; hardness about 5–6 Mohs, fine-grained crystalline texture, little cleavage, and specific gravity roughly 2.4–3.0 (lower if very vesicular).
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Physical properties
Dark gray to brown/purplish, highly porous, and typically dull to slightly vitreous; hardness about 5–6 Mohs, fine-grained crystalline texture, little cleavage, and specific gravity roughly 2.4–3.0 (lower if very vesicular).
Formation & geological history
Forms when basaltic lava cools rapidly at or near the surface, with trapped gas creating vesicles; age can range from recent volcanic eruptions to ancient volcanic terrains.
Uses & applications
Used as lightweight aggregate, roadstone, landscaping material, and abrasive; attractive pieces are collected, though this specimen is not gem-grade.
Geological facts
The holes are gas bubbles rather than fossils; purple coloration can result from oxidation, weathering, or surface staining. Vesicle interiors may later become mineral-filled, producing amygdaloidal basalt.
Field identification & locations
Identify by its low density, irregular bubble cavities, fine dark matrix, and lack of true glassy slag texture; common in volcanic regions such as Hawaii, Iceland, the western United States, and Italy.
