The kind of metamorphic rock made depends on the kind of original rock; for example, sandstone is turned to quartzite, shale is turned to slate, and limestone is turned to marble. Other kinds of metamorphic rock are named for the kinds of minerals present, the size of the grains and other textures.
At the highest grade of metamorphism, rocks begin to partially melt, at which point the boundary of metamorphic conditions is surpassed and the igneous part of the rock cycle is entered. Even though rocks remain solid during metamorphism, fluid is generally present in the microscopic spaces between the minerals.
Low grade metamorphic rocks tend to characterized by an abundance of hydrous minerals, minerals that contain water within their crystal structure. Examples of low grade hydrous minerals include clay, serpentine, and chlorite. Under low grade metamorphism many of the metamorphic minerals will not grow large enough to be seen without a microscope.
hornfels—hornfels are very hard rocks formed by contact metamorphism of shale, siltstone, or sandstone. The heat from the nearby magma "bakes" the sedimentary rocks and recrystallizes the minerals in them into a new texture that no longer breaks easily along the original sedimentary bedding planes.
Where the type of the original rock (the protolith) is discernible, the schist is usually given a name reflecting its protolith, such as schistose metasandstone. Otherwise, the names of the constituent minerals will be included in the rock name, such as quartz-felspar-biotite schist.
Schist is medium grade metamorphic rock, formed by the metamorphosis of mudstone / shale, or some types of igneous rock, to a higher degree than slate, i.e. it has been subjected to higher temperatures and pressures.
Metamorphic rocks are broadly classified as foliated or non-foliated. Non-foliated metamorphic rocks do not have aligned mineral crystals. Non-foliated rocks form when pressure is uniform, or near the surface where pressure is very low.
Common metamorphic rocks include phyllite, schist, gneiss, quartzite and marble. Foliated Metamorphic Rocks: Some kinds of metamorphic rocks -- granite gneiss and biotite schist are two examples -- are strongly banded or foliated.
schist, megascopically crystalline rock that has a highly developed schistosity, or tendency to split into layers. Banding (foliation) is typically poorly developed or absent.
What is Schist? Schist is a metamorphic rock made mostly of mica mineral, formed under the heat and compression of tectonic forces. It has mica grains large enough to see with the naked eye, which means it glitters and sparkles.
The names of most metamorphic rocks consist of compound terms: a. A combination of the names of constituent minerals; b. A name for the category of rock according to its fabric, such as phyllite, gneiss, schist, fels.
Metamorphic RocksMetamorphic rockTextureParent rockSchistFoliatedShale, granitic and volcanic rocksGneissFoliatedShale, granitic and volcanic rocksMarbleNonfoliatedLimestone, dolostoneQuartziteNonfoliatedQuartz sandstone7 more rows
How do the metamorphic rocks schist and quartzite differ? Quartzite contains the mineral quartz and schist does not. Quartzite forms from regional metamorphism and schist does not. Schist is organically formed and quartzite is not.
The word metamorphism is taken from the Greek for “change of form”; metamorphic rocks are derived from igneous or sedimentary rocks that have altered their form (recrystallized) as a result of changes in their physical environment.
(vii) What are metamorphic rocks? Answer: The type of rocks formed when igneous and sedimentary rocks experience heat and pressure are called metamorphic rocks.
There are two main types of metamorphic rocks: those that are foliated because they have formed in an environment with either directed pressure or shear stress, and those that are not foliated because they have formed in an environment without directed pressure or relatively near the surface with very little pressure ...
These three terms are schist, gneiss and granofels. The SCMR proposes that these terms are used as the fundamental root terms in the adoption of a systematic terminology. It is proposed that these terms have only a structural connotation, with no mineralogical or compositional implicationF3F. Essentially the terms
For practical purposes, it is accepted that rock names that are defined on the basis of a characteristic diagnostic mineral assemblage, may also be used for rocks that contain small amounts of retrograde or relict minerals not fitting into the definition . On the other hand the presence of small amounts of retrograde or relict minerals should not be reflected by the main name even if they are critical (see Table 1.2).
Constituent (mineral) that must be present in a rock in a certain minimum amount to satisfy the definition of a rock. The minimum amount is given in the definition of the rock term. May be present as major or minor constituent.
Ultramafic rocks containing olivine, and/or pyroxene and/or hornblende such as peridotite, harzburgite, lherzolite, wehrlite, websterite, pyroxenite and hornblendite may be formed by either metamorphic or by igneous processes and therefore fall in the common ground between metamorphic and igneous terminology. The SCMR recommends that for these rocks the definitions, based on mineral content, as given by Le Maitre (1989, 2002) should be used. These definitions are adopted without any implication to the rock genesis. When garnet or other major or minor minerals are present they should be indicated by the appropriate prefix. If it is desirable to emphasise the metamorphic nature of one of these ultramafic rocks then this should be specifically stated. Alternatively, a structural root name may be given (e.g. pyroxene-olivine gneiss, ultramafic garnet-pyroxene granofels).
In selecting the recommended specific names and name sets for use in the nomenclature scheme the SCMR relied on the work of its various Study Groups who established and defined the specific names and sets of names for their respective subjects. The conclusions of the Study Groups are contained in the series of papers in this volume, which form part of the products of the SCMR. These papers are an essential element of the nomenclature scheme: they contain a range of terms related to their area of study (e.g. the specific name sets), background information on the terms as well as figures and subsidiary flowcharts.
Symbols to indicate that minerals are either present in variable, undefined quantities, or absent. For example, muscovite-biotite-quartz-plagioclaseU+UkyaniteU+Ugarnet schist (gneiss) indicates a schist (gneiss) that may contain kyanite and/or garnet.