igneous
Vesicular basalt (likely weathered lava rock)
Basalt; chiefly plagioclase, pyroxene, and often olivine
AI-generated identification · may be incorrectFine-grained, brown weathered surface with abundant small vesicles (gas cavities) and dull earthy luster; typically hard (Mohs 5–6), dense, and lacking visible cleavage. The rounded form appears naturally weathered or possibly shaped.
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Physical properties
Fine-grained, brown weathered surface with abundant small vesicles (gas cavities) and dull earthy luster; typically hard (Mohs 5–6), dense, and lacking visible cleavage. The rounded form appears naturally weathered or possibly shaped.
Formation & geological history
Formed when basaltic lava cooled rapidly at or near Earth’s surface, trapping volcanic gas bubbles; likely Cenozoic or younger, though age cannot be determined from the image. Common in volcanic fields, lava flows, and oceanic crust.
Uses & applications
Used as crushed aggregate, road base, riprap, landscaping stone, and occasionally as a heat-retaining stone. Vesicular varieties have modest decorative and collector value.
Geological facts
Vesicles may later fill with secondary minerals such as calcite, zeolites, or quartz, forming amygdaloidal basalt. Brown coloration commonly results from oxidation and weathering of iron-bearing minerals.
Field identification & locations
Look for a dark fine-grained matrix, irregular rounded pores, high density, and no glassy or layered texture; a streak test, fresh broken surface, and magnet check can help. Common worldwide, especially Hawaii, Iceland, India, the western United States, and oceanic islands.
