Porphyritic Texture

Porphyritic textures with fine grained groundmasses many rocks with an overall fine grained texture display scattered minerals that are more than 1 mm across. The extra large mineral grains are called phenocrysts. Porphyry is an igneous rock that contains larger crystals phenocrysts in a fine grained groundmass.

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Porphyritic rocks are composed of at least two minerals having a conspicuous large difference in grain size.

Porphyritic texture. This porphyritic texture indicates that the magma sat and cooled a bit below the earth s surface thus giving time for the large crystals to grow before erupting onto the surface and cooling very quickly. Porphyritic rocks the two images below show a hand sample and a thin section of porphyritic aphanitic textured rocks. A porphyritic texture is displayed in an igneous rock containing large isolated crystals phenocrysts in a mass of fine textured crystals. A porphyritic texture is the texture of a rock with large phenocrysts and a background matrix of smaller crystals.

Porphyritic definition of pertaining to containing or resembling porphyry its texture or its structure. Porphyritic textures occur in coarse medium and fine grained igneous rocks. Feldspars augite and hornblende commonly show rectangular crystal shapes whereas. Porphyritic texture is really a subtype but usage of the term often confuses the beginner.

A porphyritic texture displays minerals in two distinct size populations. The texture of a rock in which relatively large phenocrysts with regular crystal faces are set in a generally fine grained groundmass. 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. An extrusive rock with a porphyritic texture has a groundmass that contains an unequal number of phenocrysts and consists of either microlites or glass.

Rocks with porphyritic textures may be extrusive or intrusive. K feldspar phenocrysts in this sample. Porphyritic texture porphyritic texture is an igneous rock texture in which large crystals are set in a finer grained or glassy groundmass. Usually the larger crystals known as phenocrysts formed earlier in the crystallisation sequence of the magma.

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 texture indicates that a magma has gone. One or more minerals are consistently larger than the rest of the minerals in a rock. To form this crystal contrast of smaller and larger minerals the rock likely went through different stages of cooling that formed different sizes of minerals.

Porphyritic texture is a very common texture in igneous rocks in which larger crystals phenocrysts are embedded in a fine grained groundmass.