igneous
Likely industrial slag or weathered basalt
Basaltic rock; possibly iron-rich furnace slag (diagnosis uncertain from image)
AI-generated identification · may be incorrectDark gray-black, fine-grained to glassy, with metallic-looking surfaces and irregular fractures; basalt is typically Mohs 6, dull to weakly vitreous, dense, and lacks visible cleavage. Vesicles or sharp glassy textures would favor slag.
Identified More igneous →
Explore Likely industrial slag or weathered basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-black, fine-grained to glassy, with metallic-looking surfaces and irregular fractures; basalt is typically Mohs 6, dull to weakly vitreous, dense, and lacks visible cleavage. Vesicles or sharp glassy textures would favor slag.
Formation & geological history
Basalt forms from rapidly cooled mafic lava, commonly in volcanic fields and oceanic crust; slag is a human-processed smelting byproduct and is not naturally geological. An age cannot be established from the photograph.
Uses & applications
Basalt is used as crushed aggregate, building stone, and occasionally for decorative objects; slag is mainly collected as a curiosity or used as aggregate and abrasive material.
Geological facts
The angular pieces and possible metallic/glassy texture are more suggestive of slag than ordinary basalt. A magnet, streak test, and examination for bubbles or flow textures can help distinguish them.
Field identification & locations
Common basalt occurs worldwide, especially in volcanic regions; historic slag is common near furnaces, mines, and industrial sites. Test magnetism, density, and streak, but avoid handling unknown slag because it may contain heavy metals.
