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Prehnite
Prehnite is an inosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2. Limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most often forms as stalactitic or botryoidal aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite. Very rarely will it form distinct, well-individualized crystals showing a square-like cross-section, including those found at the Jeffrey Mine in Asbestos, Quebec, Canada. Prehnite is brittle with an uneven fracture and a vitreous to pearly luster. Its hardness is 6-6.5, its specific gravity is 2.80-2.90 and its color varies from light green to yellow, but also colorless, blue, pink or white. In April 2000, rare orange prehnite was discovered in the Kalahari Manganese Fields, South Africa. Prehnite is mostly translucent, and rarely transparent. Though not a zeolite, prehnite is found associated with minerals suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laumontite
Laumontite is a mineral, one of the zeolite group. Its molecular formula is , a hydrated calcium-aluminium silicate. Potassium or sodium may substitute for the calcium but only in very small amounts. It is monoclinic, space group C2/m. It forms prismatic crystals with a diamond-shaped cross-section and an angled termination. When pure, the color is colorless or white. Impurities may color it orange, brownish, gray, yellowish, pink, or reddish. It has perfect cleavage on 10and 10and its fracture is conchoidal. It is very brittle. The Mohs scale hardness is 3.5-4. It has a vitreous luster and a white streak. It is found in hydrothermal deposits left in calcareous rocks, often formed as a result of secondary mineralization. Host rock types include basalt, andesite, metamorphic rocks and granites. It forms at a temperature of about , and becomes unstable above about , and so its presence in sedimentary rocks indicates that these have experienced intermediate diagenesis. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicate Mineral
Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually considered a silicate mineral. Silica is found in nature as the mineral quartz, and its polymorphism (materials science), polymorphs. On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working the crust for billions of years. These processes include partial melting, crystallization, fractionation, metamorphism, weathering, and diagenesis. Living organisms also contribute to this carbonate–silicate cycle, geologic cycle. For example, a type of plankton known as diatoms construct their exoskeletons ("frustules") from silica extracted from seawater. The frustules of dead diatoms are a major constituent of deep ocean sediment, and of diatomaceous e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apophyllite
The name apophyllite refers to a specific group of phyllosilicates, a class of minerals. Originally, the group name referred to a specific mineral, but was redefined in 1978 to stand for a class of minerals of similar chemical makeup that comprise a solid solution series, and includes the members fluorapophyllite-(K), fluorapophyllite-(Na), hydroxyapophyllite-(K). The name apophyllite is derived from the Greek ἀποφυλλίζω ''apophylliso,'' meaning "it flakes off", a reference to this class's tendency to flake apart when heated, due to water loss. Exfoliation of apophyllite is also possible by treating it with acids or simply by rubbing it. These minerals are typically found as secondary minerals in vesicles in basalt or other volcanic rocks. A recent change (2008) in the nomenclature system used for this group was approved by the International Mineralogical Association, removing the prefixes from the species names and using suffixes to designate the species.Burke, E.A.J. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Netherlands
) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherlands , established_title2 = Act of Abjuration , established_date2 = 26 July 1581 , established_title3 = Peace of Münster , established_date3 = 30 January 1648 , established_title4 = Kingdom established , established_date4 = 16 March 1815 , established_title5 = Liberation Day (Netherlands), Liberation Day , established_date5 = 5 May 1945 , established_title6 = Charter for the Kingdom of the Netherlands, Kingdom Charter , established_date6 = 15 December 1954 , established_title7 = Dissolution of the Netherlands Antilles, Caribbean reorganisation , established_date7 = 10 October 2010 , official_languages = Dutch language, Dutch , languages_type = Regional languages , languages_sub = yes , languages = , languages2_type = Reco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hendrik Von Prehn
Hendrik may refer to: * Hendrik (given name) * Hans Hendrik, Greenlandic Arctic traveller and interpreter * Hendrik Island, an island in Greenland * Hendrik-Ido-Ambacht, a municipality in the Netherlands * A character from ''Dragon Quest XI'' See also * Hendrich (other) * Hendrick (other) Hendrick may refer to: People * Hendrick (given name), alternative spelling of the Dutch given name Hendrik * Hendrick (surname) * King Hendrick (other), one of two Mohawk leaders who have often been conflated: ** Hendrick Tejonihokara ... * Henrich {{disambig, surname ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eastern Cape Province
The Eastern Cape is one of the provinces of South Africa. Its capital is Bhisho, but its two largest cities are East London and Gqeberha. The second largest province in the country (at 168,966 km2) after Northern Cape, it was formed in 1994 out of the Xhosa homelands or bantustans of Transkei and Ciskei, together with the eastern portion of the Cape Province. The central and eastern part of the province is the traditional home of the indigenous Xhosa people. In 1820 this area which was known as the Xhosa Kingdom began to be settled by Europeans who originally came from England and some from Scotland and Ireland. Since South Africa's early years, many Xhosas believed in Africanism and figures such as Walter Rubusana believed that the rights of Xhosa people and Africans in general, could not be protected unless Africans mobilized and worked together. As a result, the Eastern Cape is home to many anti-apartheid leaders such as Robert Sobukwe, Oliver Tambo, Nelson Mandela, Wal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cradock, Eastern Cape
Cradock is a town in the Eastern Cape Province of South Africa, in the upper valley of the Great Fish River, by road northeast of Port Elizabeth. The town is the administrative seat of the Inxuba Yethemba Local Municipality in the Chris Hani District of the Eastern Cape. The town is named after John Cradock, governor of the Cape Colony and commander of the forces. Pre-colonial history For thousands of years San hunter-gatherers were the sole human inhabitants of southern Africa. About 2000 years BP the semi-nomadic Khoikhoi (or Khoekhoen or Khoikhoin) arrived with cattle, sheep and goats. These pastoralists migrated south towards the coast. Rock paintings and petroglyphs (engravings) remain as evidence of the first people who lived here. By the 4th century AD Bantu-speaking people had begun to migrate from central Africa down the east coast into southern Africa. The amaXhosa pressed further south to the banks of the Great Fish River where they met San hunter-gatherers and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karoo System
The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a period of about 120 million years. In southern Africa, rocks of the Karoo Supergroup cover almost two thirds of the present land surface, including all of Lesotho, almost the whole of Free State, and large parts of the Eastern Cape, Northern Cape, Mpumalanga and KwaZulu-Natal Provinces of South Africa. Karoo supergroup outcrops are also found in Namibia, Eswatini, Zambia, Zimbabwe and Malawi, as well as on other continents that were part of Gondwana. The basins in which it was deposited formed during the formation and breakup of Pangea.McCarthy, T., Rubridge, B. (2005). ''The Story of Earth and Life.'' pp. 161, 187–241. Struik Publishers, Cape Town The type area of the Karoo Supergroup is the Great Karoo in South Africa, where the most exte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prehnite-pumpellyite Facies
The prehnite-pumpellyite facies is a Metamorphism, metamorphic facies typical of subseafloor alteration of the oceanic crust around mid-ocean ridge spreading centres. It is a metamorphic grade transitional between zeolite facies and greenschist facies representing a temperature range of 250 to 350 °C and a pressure range of approximately two to seven kilobars. The mineral assemblage is dependent on host composition. *In mafic rocks the assemblage is Chlorite group, chlorite, prehnite, albite, pumpellyite and epidote. *In ultramafic rocks the assemblage is Serpentine group, serpentine, talc, forsterite, tremolite and chlorite. *In Argillaceous_minerals, argillaceous sedimentary rocks the assemblage is quartz, illite, albite, and stilpnomelane chlorite. *In carbonate sediments the assemblage is calcite, Dolomite (mineral), dolomite, quartz, Clay minerals, clays, talc, and muscovite. References * Blatt, Harvey and Robert Tracy, 1995, ''Petrology: igneous, sedimentary, and me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures and pressures than schist. Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage. Gneisses are common in the ancient crust of continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct cleavage. In other words, it is a metamorphic rock composed of mineral grains easily seen with the unaided eye, which form obvious compositional layers, but which has only a weak tendency to fracture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syenite
Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, if present at all, occurs in relatively small concentrations (< 5%). Some syenites contain larger proportions of components and smaller amounts of felsic material than most granites; those are classed as being of . The equivalent of syenite is |
Granite
Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions. These range in size from dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite is typical of a larger family of ''granitic rocks'', or ''granitoids'', that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by the relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF classification), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though a few (known as leucogranites) contain almost no dark minerals. Granite is nearly alway ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
