igneous
Porphyritic Basalt or Lamprophyre
Extrusive igneous rock with visible phenocrysts
Hardness typically 6 on the Mohs scale. Colors range from dark gray to black with contrasting lighter plagioclase or pyroxene phenocrysts. Luster is dull to sub-vitreous. Aphanitic to phaneritic groundmass texture.
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Physical properties
Hardness typically 6 on the Mohs scale. Colors range from dark gray to black with contrasting lighter plagioclase or pyroxene phenocrysts. Luster is dull to sub-vitreous. Aphanitic to phaneritic groundmass texture.
Formation & geological history
Formed by the rapid cooling of magnesium- and iron-rich lava at or near the Earth's surface, often originating in volcanic settings during various geological eras.
Uses & applications
Used primarily as crushed stone for construction, aggregate in concrete, and road construction. Occasionally collected by geology enthusiasts.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and is also found extensively on the Moon and Mars as volcanic plains.
Field identification & locations
Identify by its dark, fine-grained matrix containing distinct contrasting mineral crystals. Found globally in volcanic regions and ancient lava flows.
