page_title: Porphyritic
hierarchical_section_title: Porphyritic
caption_attribution_description: English: Potassium feldspar crystals in a granite, eastern Sierra Nevada, Rock Creek Canyon, California.
context_page_description: Porphyritic is an adjective used in geology, specifically for igneous rocks, for a rock that has a distinct difference in the size of the crystals, with at least one group of crystals obviously larger than another group. Porphyritic rocks may be aphanites or extrusive rock, with large crystals or phenocrysts floating in a fine-grained groundmass of non-visible crystals, as in a porphyritic basalt, or phanerites or intrusive rock, with individual crystals of the groundmass easily distinguished with the eye, but one group of crystals clearly much bigger than the rest, as in a porphyritic granite. Most types of igneous rocks may display some degree of porphyritic texture. One main type of rock that has a porphyritic texture are porphyry, though not all porphyritic rocks are porphyries.
context_section_description: Porphyritic is an adjective used in geology, specifically for igneous rocks, for a rock that has a distinct difference in the size of the crystals, with at least one group of crystals obviously larger than another group.  Porphyritic rocks may be aphanites or extrusive rock, with large crystals or phenocrysts floating in a fine-grained groundmass of non-visible crystals, as in a porphyritic basalt, or phanerites or intrusive rock, with individual crystals of the groundmass easily distinguished with the eye, but one group of crystals clearly much bigger than the rest, as in a porphyritic granite.  Most types of igneous rocks may display some degree of porphyritic texture.  One main type of rock that has a porphyritic texture are porphyry, though not all porphyritic rocks are porphyries.
caption: Porphyritic texture in a granite.  This is an intrusive porphyritic rock.  The white, square feldspar phenocrysts are much larger than crystals in the surrounding matrix; eastern Sierra Nevada, Rock Creek Canyon, California.
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