igneous
Veined basalt (likely basalt with quartz/calcite vein)
Basalt, aphanitic mafic volcanic rock; vein minerals likely quartz (SiO₂) or calcite (CaCO₃)
AI-generated identification · may be incorrectDark gray-black, fine-grained, massive rock with a contrasting white mineral vein and subtle weathering; typical hardness is 6–7 for basalt, with quartz at 7 or calcite at 3, and generally dull to slightly vitreous luster. Basalt has no visible cleavage and commonly contains plagioclase, pyroxene, and olivine.
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Physical properties
Dark gray-black, fine-grained, massive rock with a contrasting white mineral vein and subtle weathering; typical hardness is 6–7 for basalt, with quartz at 7 or calcite at 3, and generally dull to slightly vitreous luster. Basalt has no visible cleavage and commonly contains plagioclase, pyroxene, and olivine.
Formation & geological history
Basalt forms when low-silica lava cools rapidly at or near Earth’s surface, commonly in oceanic crust, volcanic fields, and flood-basalt provinces. The pale vein formed later when mineral-rich fluids filled a fracture; the basalt may range from recent to Precambrian in age.
Uses & applications
Common basalt is used as crushed aggregate, road base, riprap, paving stone, and occasionally building or ornamental stone; this specimen is mainly suitable for education or collecting.
Geological facts
The white vein can be distinguished by testing: quartz scratches glass and does not fizz in dilute acid, whereas calcite fizzes and is easily scratched with a steel blade.
Field identification & locations
Identify it by its dark, dense, fine-grained texture and lack of large crystals; inspect for vesicles, magnetic response, and the vein’s hardness or acid reaction. Basalt is widespread worldwide, especially in Iceland, Hawaii, India, and oceanic terrains.
