igneous
Likely basalt (possibly iron-rich slag or meteorite mimic)
Basalt; chiefly plagioclase feldspar, pyroxene, and often olivine
AI-generated identification · may be incorrectDark gray to black, fine-grained, dull to weakly vitreous, with irregular fracture and possible vesicles or weathering pits; hardness about 5–6 and specific gravity roughly 2.8–3.1. The photograph alone cannot confirm texture, magnetism, or composition.
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Physical properties
Dark gray to black, fine-grained, dull to weakly vitreous, with irregular fracture and possible vesicles or weathering pits; hardness about 5–6 and specific gravity roughly 2.8–3.1. The photograph alone cannot confirm texture, magnetism, or composition.
Formation & geological history
Basalt forms when mafic lava rapidly cools at or near Earth’s surface, commonly in volcanic fields and oceanic crust; specimens may range from geologically young to billions of years old. Its rounded shape suggests stream or beach abrasion, or human preparation.
Uses & applications
Used extensively as crushed aggregate, road stone, railway ballast, riprap, and building stone; attractive polished pieces are occasionally sold as décor or teaching specimens.
Geological facts
Basalt is the most abundant volcanic rock on Earth and commonly develops hexagonal columnar joints. A strong magnet response may indicate magnetite, but does not by itself prove meteorite origin.
Field identification & locations
Look for a uniformly fine texture, small feldspar crystals, vesicles, and a streak that is generally gray; test with a magnet, streak plate, and hardness tools. Common localities include Hawaii, Iceland, India’s Deccan Traps, and oceanic islands.
