igneous
Porphyritic Basalt
Porphyritic Mafic Volcanic Rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, reddish-brown to dark gray color with distinct lighter phenocrysts, dull to sub-aphanitic luster, and fine-grained groundmass.
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Physical properties
Hardness of 6 on the Mohs scale, reddish-brown to dark gray color with distinct lighter phenocrysts, dull to sub-aphanitic luster, and fine-grained groundmass.
Formation & geological history
Formed through two-stage cooling of magma, where larger crystals (phenocrysts) grew slowly at depth before rapid surface eruption; common in volcanic regions globally.
Uses & applications
Used primarily as crushed stone in construction, aggregate for roadbeds, and occasionally as decorative landscape rock.
Geological facts
The distinct contrasting crystals are called phenocrysts, often composed of plagioclase feldspar embedded in a fine-grained matrix.
Field identification & locations
Easily identified in the field by its contrasting large light crystals within a dark, fine-grained volcanic background; commonly found in basaltic lava flows.
