Typically this will be initially described as foliated or 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. If a rock is foliated, its name is determined by the type of foliation present and the dominant minerals—for example, a kyanite schist. A rock’s texture is a description of: Size of mineral grains: fine, medium, or coarse. Metamorphic rock textures are foliated, non-foliated, or lineated are described below.. Metamorphic rock identification table. The preexisting rocks may be igneous, sedimentary, or other metamorphic rocks. The texture of a metamorphic rock is both a description of its constituent minerals along with their arrangement and size. 8.3 Regional metamorphism is more intense at depth Foliated Rock Textures Foliation is broadly defined as any planar arrangement of mineral grains or structural features in a rock. Foliation - any planar set of minerals, or banding of mineral concentrations, especially the planar structure that results from flattening of the mineral grains, like micas. Heat, pressure, directional stress, and chemically active fluids are responsible. Like igneous rocks, metamorphic rocks are classified based on texture and composition. The foliated rocks like slate, gneiss and schist are used as roofing material tabletops, staircases, etc. The foliation or layering that occurs in these rocks is because of the immense directional pressure they undergo deep within the Earth, usually along the boundary of a converging tectonic plate. Most classifications of metamorphic rocks involve first separating the rocks into two categories by their texture -foliated rocks and non-foliated rocks. Each kind of texture has a variety of different characteristics that make them unique. The most important non-foliated rock is marble. It is popular for a wide variety of uses such as roofing, flooring, and flagging because of its durability and attractive appearance. Some examples of metamorphic rocks are gneiss, slate, marble, schist, quartzite, hornblende, and phyllite. Metamorphic textures are divided into two categories: foliated and non-foliated. There are fundamental types of metamorphism: regional metamorphism and phone, or thermal, metamorphism. Textural features of metamorphic rocks have been discussed in the previous lecture. The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. The changes that occur during metamorphism may involve changes in rock texture, in the minerals present, and sometimes in overall rock composition. There are nine main types of igneous rock textures: Phaneritic, vesicular, aphanitic, porphyritic, poikilitic, glassy, pyroclastic, equigranular, and spinifex. Metamorphic Rocks: Metamorphic rocks are made through the process of intense heat and pressure that is applied to a sedimentary, metamorphic, or igneous rock. Metamorphic petrologists study metamorphic rocks to interpret those histories. Each of these will be discussed in turn, then we will summarize how metamorphic rocks are classified. Engineering Uses of Metamorphic Rocks: The metamorphic rocks are extensively used as building stones. Metamorphic rocks form by recrystallization in the solid state because of changes in temperature, pressure, or the composition of pore fluids. Planar texture can … Metamorphic rock, any rock that results from the alteration of preexisting rocks in response to changing conditions, such as variations in temperature, pressure, and mechanical stress, and the addition or subtraction of chemical components. Metamorphic Textures. Foliated metamorphic rocks. Foliation in metamorphic rocks occurs when the … • Processes leading to texture formation • Textures of Contact Metamorphism • High Strain Metamorphic Textures • Regional Metamorphic Textures • Replacement Textures and Reaction Rims 2. These changes record geologic processes and events of the past. 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. Allothimorph —a constituent of a metamorphic rock that has not changed its original crystal outline. For example : Biotite schist, hornblende schist, chlorite-granet schist, kyanite schist, etc. Furthermore, the texture of sedimentary rocks affects such derived properties of these rocks as porosity, permeability, bulk density, electrical conductivity, and sound transmissibility. Granoblastic texture: is an equigranular texture in which crystals adopt a polygonal morphology with grain triple junctions of approximately 120 degrees. 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. The formation of granoblastic textures occurs to minimise the combined surface energy of phases within a rock. Metamorphic rocks are classified by texture and by mineral composition. Foliation is described as the existence or appearance of layers. Texture In metamorphic rocks individual minerals may or may not be bounded by crystal faces. Examples of metamorphic rocks: the metamorphic rocks form in the influence of a directed stress field,! 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