Question added by Ali Al Zawad , Momentum Associate - Drilling Solutions Engineer , National Oilwell Varco Date Posted: 2014/01/25. K-feldspar phenocrysts in this sample. in addition to the other visible crystals. Porphyritic textures are found in rocks with both coarse- and fine-grained groundmasses. A plutonic rock is also called an intrusive rock as it is derived from magma that intruded the rock layers but never reached the earth’s surface. Porphyritic definition, of, pertaining to, containing, or resembling porphyry, its texture, or its structure. The crystals are clearly visible, these rocks crystallized (cooled slowly) below the Earth's surface. 2. Aphanitic is an antonym of phaneritic. 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. Phaneritic - The term phaneritic comes from the Greek (phaneros = visible, to show). A phenocryst is a large crystal that visually stands out compared to the rest of the minerals. Porphyritic texture is really a subtype, but usage of … Phaneritic textures are typical of intrusive igneous rocks, these rocks crystallized slowly below Earth's surface.. Aphanitic rocks in contrast to phaneritic rocks, typically form from lava which crystallize rapidly on or near Earth' surface Many rocks with an overall fine-grained texture display scattered minerals that are more than 1 mm across. Start studying Physical Geology Igneous Rocks. Of or containing porphyry. Porphyry is an igneous rock that contains larger crystals (phenocrysts) in a fine-grained groundmass. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Containing relatively large isolated crystals in a mass of fine texture. The minerals in a phaneritic igneous rock are sufficiently large to see each individual crystal with the naked eye. Chapter 3: Igneous Textures The texture of a rock is a result of various processes that controlled the rock’s genesis and, along with mineralogy and chemical composition, provides information that we may use to interpret the rock’s -Phaneritic- cools slowly, crystals large enough to be seen and all about the same size-Pegmatitic- unusually large crystals-Porphyritic- two different crystal sizes, two different cooling rates. Two different crystal sizes indicate two different cooling rates Porphyritic Texture the texture of a rock in which relatively large phenocrysts with regular crystal faces are set in a generally fine-grained groundmass. Phenocrysts are found in porphyritic textures where large grains are visible in volcanic extrusive rocks. Only minor amounts of quartz. 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. Large crystals in a porphyritic rock are called phenocrysts. ... Porphyritic Texture: A rock of this texture may be extrusive or intrusive. Geology Geophysics Earth Science. Granite vs Rhyolite characteristics assist us to distinguish and recognize rocks. A phaneritic rock can also be referred to as a porphyritic-phaneritic rock if the phaneritic rock contains some very large crystals (ie. In Figure 8.6 are two porphyritic rocks: a porphyritic-aphanitic basalt, and a porphyritic-phaneritic … Other articles where Phaneritic texture is discussed: rock: Classification by grain or crystal size: …term for small crystals, and phaneritic for larger ones. It occurs … Porphyritic textures develop when conditions during cooling of a magma change relatively quickly. 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