There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic. A phaneritic texture is characteristic of a(n) _____ igneous rock that cooled _____. granite, gabbro). Slow cooling allows the growth of megascopic crystals that is crystals large enough to be identified with the naked eye. Rocks so formed possess a course or phaneritic texture. Pegmatitic texture occurs during magma cooling when some minerals may grow so large that they become massive (the size ranges from a few centimetres to several metres). Similarly, a rock with small crystals probably formed at or near the surface and cooled quickly. It is recognized by its glassy texture. d. glassy. For example, a porphyritic-aphanitic texture signifies that phenocrysts occur within an aphanitic matrix. Magma that is cooling slowly and over long period of time (millions of year) will form large crystals. c. A mountain-building episode. Phaneritic Texture • Coarse grained texture • Relatively slow rate of cooling • Equigranular, interlocking crystals • Slow cooling = crystallization at depth 26. Texture: aphanitic, glassy; Composition: intermediate (andesitic) to felsic (rhyolitic) It has coarse-grained textures usually show that slowly cooled deep underground. b. This is typical of pegmatites. The individual crystals in phaneritic texture are readily visible to the unaided eye. 12 intrusive; phaneritic obsidian; felsic extrusive; aphanitic Question 7 of A _____ texture is the result of slow cooling followed by rapid cooling. Phaneritic texture is a texture in which the minerals that make up the rock can be differentiated by the naked eye. Pegmatitic texture occurs during magma cooling when some minerals may grow so large that they become massive (the size ranges from a few centimetres to several metres). aphanitic, phaneritic, porphyritic, vesicular, glassy, and pyroclastic. ... What does a porphyritic texture indicate about the cooling history of an igneous rock? Silicic magmatic compositions and fast cooling rates prevent the formation of crystals even at the microscopic scale. There are two major states of molten rock: Magma and Lava. ... or phaneritic rocks. (In contrast, the crystals in an aphanitic rock are too small to be seen with the naked eye.) A fine-grained texture is the product of rapid cooling and crystallization of lava. Porphyritic - This texture describes a rock that has well-formed crystals visible to the naked eye, called phenocrysts , set in a very fine grained or glassy matrix, called the groundmass . … IGNEOUS ROCK TEXTURES Phaneritic Texture Phaner itic textured rocks are comprised of large crystals that are clearly visible to the eye with or without a hand lens or binocular microscope. These are called intrusive rocks, and they have a phaneritic texture (from the Greek “phanerous” meaning visible). As a result, relatively large mineral grains are formed, yielding a phaneritic texture. Phaneritic texture forms when magma deep underground in the plutonic environment cools slowly, giving the crystals time to grow. Idealized rates of crystal nucleation and growth as a function of temperature below the melting point. Slow cooling results in only minor undercooling (T a), so that rapid growth and slow nucleation produce fewer coarse-grained crystals. Question 6 of Cooling rapidly at Earth’s surface gives _____ rocks an _____ texture. Phaneritic Rock Phaneritic rock is igneous rock with large, identifiable crystals of roughly equal size. These are called extrusive rocks and have an aphanitic texture (from the Greek “a-” … Groundmass may be eitheraphanitic or phaneritic. Igneous textures include the rock textures occurring in igneous rocks. This texture occurs when rocks form under the surface of the earth, longer cooling times result in larger mineral grains. They are what is known as rock grain size. Classification of Igneous Rocks. Rapid cooling permits more undercooling (T b), so that slower A phanerite is an igneous rock whose microstructure is made up of crystals large enough to be distinguished with the unaided eye. Learn how texture is influenced by the cooling rate of magma and how different mineral compositions lead to different igneous rock classifications in this video lesson. The slow cooling produces large crystals called _____; then the rapid cooling produces the surrounding rock called the _____. ... With slow cooling, the rate of growth of mineral grains exceeds the rate of nuclei formation within the minerals of the rocks. The rock began cooling under the Earth's surface, but then was moved to above the Earth's surface where it finished cooling. Igneous textures are used by geologists in determining the mode of origin igneous rocks and are used in rock classification. K-feldspar phenocrysts in this sample. 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