Metamorphic Rocks: Metamorphic rocks are made through the process of intense heat and pressure that is applied to a sedimentary, metamorphic, or igneous rock. The texture of a metamorphic rock is both a description of its constituent minerals along with their arrangement and size. Rock change may lead to changes in mineralogy, texture, and sometimes the chemical composition of rocks. It is a characteristic of foliation planes, and the rocks showing this texture are found under greenschist, amphibolite, and eclogite metamorphic facies. Phaneritic textures are where interlocking crystals of igneous rock are visible to the unaided eye. The texture of a metamorphic rock can be either foliated and appear layered or banded, or non-foliated and appear uniform in texture without banding. Here we examine only the foliated types. These can range from textures similar to the original protolith at low grades of metamorphism, to textures that are purely produced during metamorphism and leave the rock with little resemblance to the original protolith. A change in the texture, structure, or chemical composition of a rock due to contact with magma Engineering Uses of Metamorphic Rocks: The metamorphic rocks are extensively used as building stones. The foliated rocks like slate, gneiss and schist are used as roofing material tabletops, staircases, etc. Textures and Structures of Metamorphic Rocks 1. The pressure applied to the reforming rock causes the differences in the way the rock looks once recrystallized and determines whether it will be foliated or nonfoliated. Gneiss ("nice") is a rock of great variety with large mineral grains arranged in wide bands. Granoblastic texture: is an equigranular texture in which crystals adopt a polygonal morphology with grain triple junctions of approximately 120 degrees. Like igneous rocks, metamorphic rocks are classified based on texture and composition. Arrangement of mineral grains: aligned or un-aligned (massive or homogeneous). It is composed primarily of the mineral calcite (CaCO 3 ) and usually contains other minerals, such as clay minerals, micas, quartz , pyrite , iron oxides, and graphite . The following are textures, or terms used in relation to textures, of metamorphic rocks; * indicates an illustration in the cross-reference. Metamorphic rocks exhibit a variety of textures. Metamorphic texture is the description of the shape and orientation of mineral grains in a metamorphic rock. It is popular for a wide variety of uses such as roofing, flooring, and flagging because of its durability and attractive appearance. Metamorphic rock - Metamorphic rock - Classification of metamorphic rocks: Because of the diverse chemistry, mineralogy, and primary origin of metamorphic rocks and because of the diverse fabrics or textures that may develop depending on the stresses that may operate during their formation, there is no simple, universally used classification of these rocks. Metamorphic rocks are eventually exposed at the surface by uplift and erosion of the overlying rock. 6.2 Metamorphic textures . Metamorphic textures are either granular or foliated. Strong foliation in fine-grained metamorphic rocks. Foliated Rock Textures Foliation is broadly defined as any planar arrangement of mineral grains or structural features in a rock. All images have two views, in plane- and cross-polarized light. Texture In metamorphic rocks individual minerals may or may not be bounded by crystal faces. The preexisting rocks may be igneous, sedimentary, or other metamorphic rocks. … [2] Porphyritic texture is one in which larger pieces ( phenocrysts ) are embedded in a background mass made of much finer grains. Heat, pressure, directional stress, and chemically active fluids are responsible. Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. The texture and structure of metamorphic rocks represent the fundamental knowledge of metamorphic petrology. The subsequent chapters describe the structural classification of grain … Each kind of texture has a variety of different characteristics that make them unique. Planar texture can … There are two basic types of texture for a metamorphic rock. The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. It means a type of rock texture, not a composition. The texture of metamorphic rocks is foliated due to pressure. If the minerals are segregated into alternating light‐colored and dark‐colored layers, the rock is called a gneiss. Some examples of metamorphic rocks are gneiss, slate, marble, schist, quartzite, hornblende, and phyllite. Metamorphic rock can also be formed from tectonic processes such as continental collisions. Metamorphic textures are divided into two categories: foliated and non-foliated. Along with other properties of these rocks, it helps to characterize and distinguish them from other types of rocks and it aids in their correlation. Metamorphic Textures provides definitions, descriptions and illustrations of metamorphic textures, as well as the fundamental processes involved in textural development.This book is composed of 11 chapters and begins with a presentation of the metamorphic processes and the production of metamorphic minerals. Metamorphic rocks form by recrystallization in the solid state because of changes in temperature, pressure, or the composition of pore fluids. Metamorphic rock textures are foliated, non-foliated, or lineated are described below.. Metamorphic rock identification table. Furthermore, the texture of sedimentary rocks affects such derived properties of these rocks as porosity, permeability, bulk density, electrical conductivity, and sound transmissibility. The process where one type of rock changes into metamorphic rock because of chemical processes or changes in temperature and pressure Define contact metamorphism. Metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (), without the protolith melting into liquid magma (a solid-state change). Allothimorph —a constituent of a metamorphic rock that has not changed its original crystal outline. Rock-forming minerals of metamorphic rocks, in thin section (a work in progress) 1 Olivine: forsterite Olivine: Forsterite, in marble. , pressure, directional stress, and bulk chemical composition of rocks is based texture! 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