igneous
Possible slag or basalt fragment
Indeterminate dark mafic material; likely basalt (plagioclase–pyroxene) or industrial iron-rich slag
AI-generated identification · may be incorrectDark gray-black, glossy to dull luster, irregular vesicular surface, and no visible crystal structure; estimated hardness 5–6 if basalt, but slag may be softer or glassier. Cleavage is not apparent and specific gravity appears moderate to high.
Identified More igneous →
Explore Possible slag or basalt fragment in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-black, glossy to dull luster, irregular vesicular surface, and no visible crystal structure; estimated hardness 5–6 if basalt, but slag may be softer or glassier. Cleavage is not apparent and specific gravity appears moderate to high.
Formation & geological history
If basalt, it formed from rapidly cooled mafic lava, commonly during the Cenozoic or older volcanic episodes. The rounded, highly glossy texture could instead indicate human-produced smelting slag, which is not a natural rock.
Uses & applications
Basalt is used as aggregate, dimension stone, and occasionally in polished specimens; slag has industrial and historical interest but little jewelry value.
Geological facts
The image alone cannot reliably distinguish basalt from slag; metallic-looking flow textures, bubbles, and unusually glassy surfaces favor slag.
Field identification & locations
Check for abundant vesicles, metallic beads, magnetic response, and a glassy flow texture—these favor slag; fine-grained, uniformly crystalline texture favors basalt. Common basalt sources include volcanic regions worldwide.
