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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] |
Andalusite
Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5. This mineral was called andalousite by Delamétehrie, who thought it came from Andalusia, Spain. It soon became clear that it was a locality error, and that the specimens studied were actually from El Cardoso de la Sierra, in the Spanish province of Guadalajara, not Andalusia. Andalusite is trimorphic with kyanite and sillimanite, being the lower pressure mid temperature polymorph. At higher temperatures and pressures, andalusite may convert to sillimanite. Thus, as with its other polymorphs, andalusite is an aluminosilicate index mineral, providing clues to depth and pressures involved in producing the host rock. Varieties The variety chiastolite commonly contains dark inclusions of carbon or clay which form a cruciform pattern when shown in cross-section. This stone was known at least from the sixteenth century, being taken to many European countries, as a souvenir, by pilgrims returning from Sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fruchtschiefer
Fruchtschiefer is a local variety of contact metamorphic rock that is derived from argillite. Formation and mineral content Fruchtschiefer is formed under very low pressure (low grade metamorphic rock) and temperatures of ca. 500 °C. At these temperatures cordierite grows to the size of grains of corn, which is where its name comes from; ''Frucht'' being German for "corn" (as well as "fruit"). It contains the following minerals: cordierite, muscovite, potassium feldspar, quartz, biotite and hornblende. Occurrence Fruchtschiefer occurs in Germany as contact metamorphic rock in the Harz, Ore Mountains, Odenwald and Vogtland. The best known deposits are those near Theuma and Tirpersdorf. Their protoliths originate from the Ordovician period. Rocks quarried here have been used well beyond the local region.Heiner Siedel, Ferdinand Heinz: ''Der Abbau von Fruchtschiefer im Gebiet um Theuma und Tirpersdorf im sächsischen Vogtland und seine Verwendung''. in: Veröffentlichun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contact Metamorphic
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chemically active fluids, but the rock remains mostly solid during the transformation. Metamorphism is distinct from weathering or diagenesis, which are changes that take place at or just beneath Earth's surface. Various forms of metamorphism exist, including regional, contact, hydrothermal, shock, and dynamic metamorphism. These differ in the characteristic temperatures, pressures, and rate at which they take place and in the extent to which reactive fluids are involved. Metamorphism occurring at increasing pressure and temperature conditions is known as ''prograde metamorphism'', while decreasing temperature and pressure characterize ''retrograde metamorphism''. Metamorphic petrology is the study of metamorphism. Metamorphic petrologists re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large scale (300 kton/year, in 1989) for uses in pencils, lubricants, and electrodes. Under high pressures and temperatures it converts to diamond. It is a weak conductor of heat and electricity. Types and varieties Natural graphite The principal types of natural graphite, each occurring in different types of ore deposits, are * Crystalline small flakes of graphite (or flake graphite) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken. When broken the edges can be irregular or angular; * Amorphous graphite: very fine flake graphite is sometimes called amorphous; * Lump graphite (or vein graphite) occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nodule (geology)
In sedimentology and geology, a nodule is a small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition, such as a pyrite nodule in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale, from the enclosing sediment or sedimentary rock. Normally, a nodule has a warty or knobby surface and exists as a discrete mass within the host strata. In general, they lack any internal structure except for the preserved remnants of original bedding or fossils. Nodules are closely related to concretions and sometimes these terms are used interchangeably. Minerals that typically form nodules include calcite, chert, apatite (phosphorite), anhydrite, and pyrite.Neuendorf, KKE, JP Mehl, Jr., and JA Jackson, eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. Boggs S, Jr. (2009) ''Petrology of Sedimentary Rocks.'' Cambridge University Press, Cambridge, Unite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in sedimentary rock. It is particularly prominent in many granites, pegmatites, and schists, and "books" (large individual crystals) of mica several feet across have been found in some pegmatites. Micas are used in products such as drywalls, paints, fillers, especially in parts for automobiles, roofing and shingles, as well as in electronics. The mineral is used in cosmetics and food to add "shimmer" or "frost." Properties and structure The mica group is composed of 37 phyllosilicate minerals. All crystallize in the monoclinic system, with a tendency towards pseudohexagonal crystals, and are similar in structure but vary in chemical composition. Micas are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
