A

David

Darling

porphyry

porphyritic granite

Porphyritic granite.


Porphyry is a hard igneous rock having many large crystals (phenocrysts) set in a very fine-grained matrix, occurring in dikes and sills. More generally, rocks are said to have a porphyritic texture if they contain some phenocrysts in a finer-grained matrix (e.g., porphyritic granite, as shown here).