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Knotenschiefer
Knotenschiefer is a variety of spotted slate characterized by conspicuous subspherical or polyhedral clots that are often individual minerals such as cordierite, biotite, Chlorite group, chlorite, andalusite and others.Bucksch, Herbert (1997). ''Dictionary of Geotechnical Engineering'', Vol. 2., Springer-Verlag, Berlin. . Like fleckschiefer, fruchtschiefer and garbenschiefer, knotenschiefer is a variety of contact metamorphic slate. It is formed at temperatures of around 400 °C and its dark coloration is caused by graphite. Fruchtschiefer occurs at 500 °C. Knotenschiefer is characterised by small Nodule (geology), nodules, up to one centimetre in size, and nodular deposits of mica as a result of the growth in grain size during metamorphism. The nodules consist of iron minerals, carbon substances and mica; as the metamorphic temperature rises, minerals such as andalusite or chiastolite increasingly occur. References * Walter Maresch, Olaf Medenbach: ''Steinbachs Natu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Knotenschiefer
Knotenschiefer is a variety of spotted slate characterized by conspicuous subspherical or polyhedral clots that are often individual minerals such as cordierite, biotite, Chlorite group, chlorite, andalusite and others.Bucksch, Herbert (1997). ''Dictionary of Geotechnical Engineering'', Vol. 2., Springer-Verlag, Berlin. . Like fleckschiefer, fruchtschiefer and garbenschiefer, knotenschiefer is a variety of contact metamorphic slate. It is formed at temperatures of around 400 °C and its dark coloration is caused by graphite. Fruchtschiefer occurs at 500 °C. Knotenschiefer is characterised by small Nodule (geology), nodules, up to one centimetre in size, and nodular deposits of mica as a result of the growth in grain size during metamorphism. The nodules consist of iron minerals, carbon substances and mica; as the metamorphic temperature rises, minerals such as andalusite or chiastolite increasingly occur. References * Walter Maresch, Olaf Medenbach: ''Steinbachs Natu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slate
Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression. The foliation in slate is called "slaty cleavage". It is caused by strong compression causing fine grained clay flakes to regrow in planes perpendicular to the compression. When expertly "cut" by striking parallel to the foliation, with a specialized tool in the quarry, many slates will display a property called fissility, forming smooth flat sheets of stone which have long been used for roofing, floor tiles, and other purposes. Slate is frequently grey in color, especially when seen, en masse, covering roofs. However, slate occurs in a variety of colors even from a single locality; for ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cordierite
Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: to . A high-temperature polymorph exists, indialite, which is isostructural with beryl and has a random distribution of Al in the rings. Name and discovery Cordierite, which was discovered in 1813, in specimens from Níjar, Almería, Spain, is named after the French geologist Louis Cordier (1777–1861). Occurrence Cordierite typically occurs in contact or regional metamorphism of pelitic rocks. It is especially common in hornfels produced by contact metamorphism of pelitic rocks. Two common metamorphic mineral assemblages include sillimanite-cordierite-spinel and cordierite-spinel-plagioclase- orthopyroxene. Other associated minerals include garnet (cordierite-garnet-sillimanite gneisses) and anthophyllite. Cordierite also occurs in some granites, pegm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biotite
Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous end-members include siderophyllite and eastonite. Biotite was regarded as a mineral ''species'' by the International Mineralogical Association until 1998, when its status was changed to a mineral ''group''. The term ''biotite'' is still used to describe unanalysed dark micas in the field. Biotite was named by J.F.L. Hausmann in 1847 in honor of the French physicist Jean-Baptiste Biot, who performed early research into the many optical properties of mica. Members of the biotite group are sheet silicates. Iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. The term "iron mica" is sometimes used for iron-rich biotite, but the term also refers to a flaky micaceous form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorite Group
The chlorites are the group of phyllosilicate minerals common in low-grade metamorphic rocks and in altered igneous rocks. Greenschist, formed by metamorphism of basalt or other low-silica volcanic rock, typically contains significant amounts of chlorite. Chlorite minerals show a wide variety of compositions, in which magnesium, iron, aluminium, and silicon substitute for each other in the crystal structure. A complete solid solution series exists between the two most common end members, magnesium-rich clinochlore and iron-rich chamosite. In addition, manganese, zinc, lithium, and calcium species are known. The great range in composition results in considerable variation in physical, optical, and X-ray properties. Similarly, the range of chemical composition allows chlorite group minerals to exist over a wide range of temperature and pressure conditions. For this reason chlorite minerals are ubiquitous minerals within low and medium temperature metamorphic rocks, some igneous r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
