igneous
Dark tumbled stone, possibly basalt
Basalt (fine-grained mafic volcanic rock; identification tentative from the image)
AI-generated identification · may be incorrectAppears dark gray-green to brown, dull to subtly waxy, fine-grained, and rounded/hand-shaped; likely Mohs hardness about 5–6. No visible crystals, cleavage, or diagnostic banding can be resolved.
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Physical properties
Appears dark gray-green to brown, dull to subtly waxy, fine-grained, and rounded/hand-shaped; likely Mohs hardness about 5–6. No visible crystals, cleavage, or diagnostic banding can be resolved.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava rapidly cools at or near Earth’s surface, commonly in oceanic crust, volcanic fields, and ancient lava flows. Its age cannot be determined from the photograph.
Uses & applications
Used as aggregate, road stone, paving, ballast, and occasionally as a polished decorative or massage stone; this small specimen has modest collecting value.
Geological facts
The shape may reflect natural weathering or human tumbling/polishing. Similar dark materials—including andesite, serpentinite, and slag—can look alike in a blurry photograph.
Field identification & locations
Common in volcanic regions worldwide; test for a dull streak, lack of glassy conchoidal fracture, and moderate hardness, and inspect a fresh surface for tiny interlocking crystals. A magnet, streak, density, and acid test would improve identification.
