igneous
Porphyritic Basalt
Extrusive igneous rock with plagioclase phenocrysts
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark brown to black groundmass with lighter white or grey plagioclase phenocrysts, dull luster, aphanitic texture.
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Physical properties
Hardness of 6 on the Mohs scale, dark brown to black groundmass with lighter white or grey plagioclase phenocrysts, dull luster, aphanitic texture.
Formation & geological history
Formed from rapidly cooling lava flows at the Earth's surface where early-formed crystals grew larger before the final groundmass solidified rapidly.
Uses & applications
Used in construction, aggregate, road base, and landscaping materials.
Geological facts
Porphyritic textures indicate a two-stage cooling history, starting slowly underground and finishing quickly on the surface.
Field identification & locations
Identify by contrasting large mineral crystals embedded within a very fine-grained dark matrix; commonly found in volcanic regions worldwide.
