igneous
Dark gray rock, possibly basalt or slate
Undetermined from image; likely fine-grained basalt (mafic volcanic rock)
AI-generated identification · may be incorrectDark gray, dull to slightly lustrous, with irregular fractures and no clearly visible crystals. If basalt: typically Mohs 5–6, specific gravity about 2.8–3.0; the image does not show enough detail to confirm mineral composition or cleavage.
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Physical properties
Dark gray, dull to slightly lustrous, with irregular fractures and no clearly visible crystals. If basalt: typically Mohs 5–6, specific gravity about 2.8–3.0; the image does not show enough detail to confirm mineral composition or cleavage.
Formation & geological history
Basalt forms when mafic lava cools at or near Earth’s surface; its age and formation environment cannot be determined from the photograph.
Uses & applications
Basalt is used as crushed aggregate, road stone, and building stone; large uncharacterized specimens may have landscaping or collecting value.
Geological facts
The block’s angular breaks and dark color are consistent with several rocks, including basalt and slate, so a confident identification requires closer inspection or testing.
Field identification & locations
Check for fine-grained texture and hardness: basalt usually has tiny interlocking crystals and can scratch glass, while slate splits into flat sheets. Common basalt occurs in volcanic regions worldwide; value is typically about $0–$50 for an ordinary field specimen.
