igneous
Likely basalt fragment
Basalt; primarily plagioclase feldspar, pyroxene, and commonly olivine
AI-generated identification · may be incorrectDark gray-to-black, fine-grained, dull to slightly vitreous luster; hardness about 5–6 Mohs, no obvious cleavage, and typically dense (specific gravity ~2.8–3.0). The image is too limited for confident mineral-level identification.
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Physical properties
Dark gray-to-black, fine-grained, dull to slightly vitreous luster; hardness about 5–6 Mohs, no obvious cleavage, and typically dense (specific gravity ~2.8–3.0). The image is too limited for confident mineral-level identification.
Formation & geological history
Basalt forms when mafic lava rapidly cools at or near Earth’s surface, commonly in volcanic fields, oceanic crust, and flood-basalt provinces; specimens may range from very young to billions of years old.
Uses & applications
Used extensively as crushed aggregate, road base, railroad ballast, concrete additive, building stone, and occasionally as a decorative or lapidary material.
Geological facts
Its dark color reflects abundant iron- and magnesium-rich minerals. Vesicles, if present, indicate gas bubbles in cooling lava; this specimen appears compact but could also be a dark mafic mineral fragment.
Field identification & locations
Look for a fine, interlocking texture, high density, dark color, and lack of visible large crystals; a streak test, fresh fracture, and hand lens would improve identification. Common worldwide, especially near volcanic regions.
