igneous
Vesicular basalt (possibly gold-bearing or mineral-veined basalt)
Basalt, a mafic volcanic rock composed chiefly of plagioclase feldspar, clinopyroxene, and often olivine
AI-generated identification · may be incorrectDark gray-black, fine-grained, dull to weakly subvitreous, with rounded vesicles (gas cavities) and a yellow metallic-looking vein or coating. Hardness is typically about 5–6 Mohs; no obvious cleavage; specific gravity about 2.8–3.0.
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Physical properties
Dark gray-black, fine-grained, dull to weakly subvitreous, with rounded vesicles (gas cavities) and a yellow metallic-looking vein or coating. Hardness is typically about 5–6 Mohs; no obvious cleavage; specific gravity about 2.8–3.0.
Formation & geological history
Forms when low-silica lava cools rapidly at or near Earth’s surface, commonly in lava flows; ages range from recent eruptions to Precambrian. The yellow material may be sulfide, iron staining, or an applied coating, and cannot be identified reliably from the image.
Uses & applications
Common basalt is used as aggregate, paving stone, building stone, and mineral specimens; attractive pieces may be collected. It is generally not a gemstone unless the vein proves to be valuable mineralization.
Geological facts
Vesicles distinguish volcanic basalt from most intrusive mafic rocks. A true gold vein would be soft, dense, malleable, and non-crystalline; visual color alone is insufficient—acid, streak, hardness, and specific-gravity tests or assay are needed.
Field identification & locations
Look for fine grain, dark color, vesicles, and abundant plagioclase/pyroxene; common worldwide in volcanic regions. Estimated value: $2–$20 as a common specimen, potentially higher only if testing confirms gold or an unusual mineral vein.
