igneous
Weathered basaltic rock (probable basalt)
Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine
AI-generated identification · may be incorrectFine-grained, dark gray-brown, dull to earthy luster, with weathering staining and no visible cleavage; hardness about 5–6 Mohs and specific gravity roughly 2.8–3.1. The image does not show enough detail for confident mineral identification.
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Physical properties
Fine-grained, dark gray-brown, dull to earthy luster, with weathering staining and no visible cleavage; hardness about 5–6 Mohs and specific gravity roughly 2.8–3.1. The image does not show enough detail for confident mineral identification.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface, commonly in volcanic fields, oceanic crust, and flood-basalt provinces. Its exact age cannot be determined from appearance alone; it may range from recent to billions of years old.
Uses & applications
Used as crushed aggregate, road base, railroad ballast, concrete aggregate, building stone, and occasionally as a lapidary or display specimen.
Geological facts
Iron-bearing minerals commonly weather basalt to brown, yellow, or reddish surfaces. Vesicles may be hidden by weathering, but this specimen appears relatively dense and massive.
Field identification & locations
Look for a dense fine-grained texture, dark mafic color, and weak or absent visible crystals; a streak, hardness, magnetism, and acid test would help distinguish it from iron-rich sedimentary rock or slag. Common worldwide, especially volcanic regions.
