igneous
Red porphyritic volcanic rock, likely rhyolite or andesite
Porphyritic rhyolite–andesite; predominantly quartz/feldspar with iron-oxide staining
AI-generated identification · may be incorrectFine-grained volcanic matrix with scattered pale phenocrysts and strong red hematite coloration; hardness about 6–7, dull to weakly vitreous luster, no obvious cleavage. The surrounding gravel includes mixed rock fragments, so exact identification from the image is limited.
Identified More igneous →
Explore Red porphyritic volcanic rock, likely rhyolite or andesite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Fine-grained volcanic matrix with scattered pale phenocrysts and strong red hematite coloration; hardness about 6–7, dull to weakly vitreous luster, no obvious cleavage. The surrounding gravel includes mixed rock fragments, so exact identification from the image is limited.
Formation & geological history
Formed when silica-rich lava cooled relatively quickly at or near Earth’s surface, commonly during volcanic episodes from the Precambrian to Cenozoic. Red color typically reflects oxidation of iron-bearing minerals during weathering.
Uses & applications
Used locally as crushed aggregate, road base, landscaping stone, and occasionally decorative facing stone; generally little jewelry value.
Geological facts
Porphyritic texture records two cooling stages: crystals formed slowly underground, followed by rapid eruption and cooling. Red volcanic rocks may also be altered tuff or weathered andesite.
Field identification & locations
Look for a dense fine matrix containing larger feldspar or quartz crystals; a steel knife usually scratches poorly, while quartz-rich areas resist scratching. Common worldwide in volcanic belts.
