igneous
Dark mafic igneous rock, likely basalt or gabbro
Basalt–gabbroic rock; chiefly plagioclase feldspar and pyroxene, possibly olivine
AI-generated identification · may be incorrectHardness about 5–6 Mohs; dark gray to greenish-black, dull to weakly vitreous luster, and fine- to medium-grained crystalline texture. No obvious cleavage is visible; apparent pale grains may be feldspar or weathered mineral surfaces.
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Physical properties
Hardness about 5–6 Mohs; dark gray to greenish-black, dull to weakly vitreous luster, and fine- to medium-grained crystalline texture. No obvious cleavage is visible; apparent pale grains may be feldspar or weathered mineral surfaces.
Formation & geological history
Mafic magma crystallized from iron- and magnesium-rich melt: rapid cooling produces basalt, while slow underground cooling produces gabbro. Exact age and formation setting cannot be determined from the photograph.
Uses & applications
Used as crushed aggregate, roadstone, riprap, and occasionally dimension stone; attractive fine specimens may be collected but are generally not jewelry material.
Geological facts
Basalt is the most common volcanic rock and forms much of oceanic crust; gabbro is its coarse-grained intrusive equivalent.
Field identification & locations
Identify by high density, dark color, granular texture, and resistance to scratching; a glassy surface suggests basalt, while clearly visible interlocking grains suggest gabbro. Common worldwide, especially volcanic regions and oceanic terranes.
