Porphyritic

Igneous rock with large and small crystals

Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning all types of igneous rocks can display some degree of porphyritic texture. Most porphyritic rocks have bimodal size ranges, meaning the rock is composed of two distinct sizes of crystal.

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