igneous
Porphyritic Basalt
Porphyritic Extrusive Igneous Rock
AI-generated identification · may be incorrectHardness of 6 on Mohs scale; dark brown to black groundmass with prominent lighter plagioclase feldspar phenocrysts; aphanitic texture with large crystals.
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Physical properties
Hardness of 6 on Mohs scale; dark brown to black groundmass with prominent lighter plagioclase feldspar phenocrysts; aphanitic texture with large crystals.
Formation & geological history
Formed through two-stage cooling of volcanic magma, initially slow deep underground allowing large crystals to form, followed by rapid eruption and cooling on the surface.
Uses & applications
Used in construction, as crushed aggregate for road building, and as decorative dimension stone.
Geological facts
The distinct large crystals embedded in a fine-grained matrix are called phenocrysts. This rock type is commonly found in ancient and modern volcanic regions worldwide.
Field identification & locations
Identify by its dark, fine-grained base dotted with distinct white or grey mineral crystals. Frequently found in volcanic provinces and glacial drift deposits.
