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Nyerereite
Nyerereite is a very rare sodium calcium carbonate mineral with formula Na2 Ca( C O3)2. It forms colorless, platey pseudohexagonal orthorhombic crystals that are typically twinned. It has a specific gravity of 2.54 and indices of refraction of nα=1.511, nβ=1.533 and nγ=1.535. Nyerereite is not stable in contact with the atmosphere and rapidly breaks down. Collection specimens must be kept in a sealed argon environment. It has a Hermann–Mauguin notation of mm2 and the respective space group is Cmc21. In nature Nyerereite is naturally twinned and is pseudohexagonal with triad twinning; meaning that this is a six sided crystal that apparently has a hexagonal shape but is not in the hexagonal system. Triad twinning is the intergrowth of three orthorhombic crystals that turn at their center and form hexagonally shaped crystals. Nyerereite is biaxial negative, and has a 2v of 29 degrees. It shows a center acute bisectrix and a birefringence of approximately 0.023.Mckie, D., Fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gregoryite
Gregoryite is an anhydrous carbonate mineral that is rich in potassium and sodium with the chemical formula . It is one of the two main ingredients of natrocarbonatite, found naturally in the lava of Ol Doinyo Lengai volcano, the other being nyerereite. Because of its anhydrous nature, gregoryite reacts quickly with the environment, causing the dark lava to be converted to white substance within hours. Gregoryite was first described in 1980 and named after the British geologist and author John Walter Gregory (1864–1932), who studied the East African Rift Valley. It occurs associated with nyerereite, alabandite, halite, sylvite, fluorite and calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on .... References {{Reflist Calc-alkaline rocks Hexagonal minerals Minerals in spa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonatite
Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification. Carbonatites usually occur as small volcanic plug, plugs within zoned alkalic intrusive complexes, or as dike (geology), dikes, sill (geology), sills, breccias, and vein (geology), veins. They are almost exclusively associated with continental rift-related tectonic settings. It seems that there has been a steady increase in the carbonatitic igneous activity through the Earth's history, from the Archean Eon (geology), eon to the present. Nearly all carbonatite occurrences are intrusives or subvolcanic rock, subvolcanic intrusives. This is because carbonatite lava flows, being composed largely of soluble carbonates, are easily weathered and are therefore unlikely to be preserved in the geologic record. Carbonatite erupti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ol Doinyo Lengai
Ol Doinyo Lengai (Oldoinyo Lengai), "Mountain of God" in the Maasai language, is an active volcano located in the Gregory Rift, south of Lake Natron within the Arusha Region of Tanzania, Africa. Part of the volcanic system of the East African Rift, it uniquely produces natrocarbonatite lava. The 1960 eruption of Ol Doinyo Lengai led to geological investigations that finally confirmed the view that carbonatite rock is derived from magma. Geology Ol Doinyo Lengai is unique among active volcanoes in that it produces natrocarbonatite lava, a unique occurrence of volcanic carbonatite. A few older extinct carbonatite volcanoes are located nearby, including Homa Mountain. Lava Whereas most lavas are rich in silicate minerals, the lava of Ol Doinyo Lengai is a carbonatite. It is rich in the rare sodium and potassium carbonates, nyerereite and gregoryite. Due to this unusual composition, the lava erupts at relatively low temperatures of approximately . This temperature is so low that the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonate Mineral
Carbonate minerals are those minerals containing the carbonate ion, . Carbonate divisions Anhydrous carbonates *Calcite group: trigonal **Calcite CaCO3 **Gaspéite (Ni,Mg,Fe2+)CO3 **Magnesite MgCO3 **Otavite CdCO3 **Rhodochrosite MnCO3 **Siderite FeCO3 **Smithsonite ZnCO3 **Spherocobaltite CoCO3 *Aragonite group: orthorhombic **Aragonite CaCO3 **Cerussite PbCO3 **Strontianite SrCO3 **Witherite BaCO3 **Rutherfordine UO2CO3 **Natrite Na2CO3 Anhydrous carbonates with compound formulas *Dolomite group: trigonal **Ankerite CaFe(CO3)2 **Dolomite (mineral), Dolomite CaMg(CO3)2 **Huntite Mg3Ca(CO3)4 **Minrecordite CaZn(CO3)2 **Barytocalcite BaCa(CO3)2 Carbonates with hydroxyl or halogen *Carbonate with hydroxide: monoclinic **Azurite Cu3(CO3)2(OH)2 **Hydrocerussite Pb3(CO3)2(OH)2 **Malachite Cu2CO3(OH)2 **Rosasite (Cu,Zn)2CO3(OH)2 **Phosgenite Pb2(CO3)Cl2 **Hydrozincite Zn5(CO3)2(OH)6 **Aurichalcite (Zn,Cu)5(CO3)2(OH)6 Hydrated carbonates *Hydromagnesite Mg5(CO3)4(OH)2.4H2O *Ikaite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexagonal Crystal System
In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crystal system and the rhombohedral lattice system are not equivalent (see section crystal systems below). In particular, there are crystals that have trigonal symmetry but belong to the hexagonal lattice (such as α-quartz). The hexagonal crystal family consists of the 12 point groups such that at least one of their space groups has the hexagonal lattice as underlying lattice, and is the union of the hexagonal crystal system and the trigonal crystal system. There are 52 space groups associated with it, which are exactly those whose Bravais lattice is either hexagonal or rhombohedral. __TOC__ Lattice systems The hexagonal crystal family consists of two lattice systems: hexagonal and rhombohedral. Each lattice system consists of one Bravais l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the world, with its internationally recognised territory covering , and encompassing one-eighth of Earth's inhabitable landmass. Russia extends across Time in Russia, eleven time zones and shares Borders of Russia, land boundaries with fourteen countries, more than List of countries and territories by land borders, any other country but China. It is the List of countries and dependencies by population, world's ninth-most populous country and List of European countries by population, Europe's most populous country, with a population of 146 million people. The country's capital and List of cities and towns in Russia by population, largest city is Moscow, the List of European cities by population within city limits, largest city entirely within E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kola Peninsula
sjd, Куэлнэгк нёа̄ррк , image_name= Kola peninsula.png , image_caption= Kola Peninsula as a part of Murmansk Oblast , image_size= 300px , image_alt= , map_image= Murmansk in Russia.svg , map_caption = Location of Murmansk Oblast within Russia , location= Northwest Russia , coordinates= , area_km2= 100000 , length_km= 370 , width_km= 244 , highest_mount= Yudychvumchorr , elevation_m= 1201 , waterbody = * Barents Sea * White Sea , country= Russia , country_admin_divisions_title= Oblast , country_admin_divisions= Murmansk Oblast , density_km2= , demonym= , population= , citizenships= The Kola Peninsula (russian: Кольский полуостров, Kolsky poluostrov; sjd, Куэлнэгк нёа̄ррк) is a peninsula in the extreme northwest of Russia, and one of the largest peninsulas of Europe. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely inside the Arctic Circle and is bordered by the Barents Sea to the n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intrusive Rock
Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form ''Igneous intrusion, intrusions'', such as batholiths, dike (geology), dikes, Sill (geology), sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March 27, 2017.Igneous intrusive rocks, accessdate: March 27, 2017.Britannica.comintrusive rock , geology , Britannica.com accessdate: March 27, 2017. Intrusion is one of the two ways igneous rock can form. The other is extrusive rock, extrusion, such as a Types of volcanic eruptions, volcanic eruption or similar event. An intrusion is any body of intrusive igneous rock, formed from magma that cools and solidifies within the crust of the planet. In contrast, an ''extrusion'' consists of extrusive rock, formed above the surface of the crust. Some geologists use the term plutonic rock synonymously with intrusive rock, but other geologists subdivide intrusive rock, by crystal size, into coarse-grai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Julius Nyerere
Julius Kambarage Nyerere (; 13 April 1922 – 14 October 1999) was a Tanzanian anti-colonial activist, politician, and political theorist. He governed Tanganyika as prime minister from 1961 to 1962 and then as president from 1962 to 1964, after which he led its successor state, Tanzania, as president from 1964 to 1985. He was a founding member and chair of the Tanganyika African National Union (TANU) party, and of its successor Chama Cha Mapinduzi, from 1954 to 1990. Ideologically an African nationalist and African socialist, he promoted a political philosophy known as Ujamaa. Born in Butiama, Mara, then in the British colony of Tanganyika, Nyerere was the son of a Zanaki chief. After completing his schooling, he studied at Makerere College in Uganda and then Edinburgh University in Scotland. In 1952 he returned to Tanganyika, married, and worked as a school teacher. In 1954, he helped form TANU, through which he campaigned for Tanganyikan independence from the British Em ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tanzania
Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and the Indian Ocean to the east; Mozambique and Malawi to the south; Zambia to the southwest; and Rwanda, Burundi, and the Democratic Republic of the Congo to the west. Mount Kilimanjaro, Africa's highest mountain, is in northeastern Tanzania. According to the United Nations, Tanzania has a population of million, making it the most populous country located entirely south of the equator. Many important hominid fossils have been found in Tanzania, such as 6-million-year-old Pliocene hominid fossils. The genus Australopithecus ranged across Africa between 4 and 2 million years ago, and the oldest remains of the genus ''Homo'' are found near Lake Olduvai. Following the rise of '' Homo erectus'' 1.8 million years ago, humanity spread ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from . The volcanic rock resulting from subsequent cooling is also often called ''lava''. A lava flow is an outpouring of lava during an effusive eruption. (An explosive eruption, by contrast, produces a mixture of volcanic ash and other fragments called tephra, not lava flows.) The viscosity of most lava is about that of ketchup, roughly 10,000 to 100,000 times that of water. Even so, lava can flow great distances before cooling causes it to solidify, because lava exposed to air quickly develops a solid crust that insulates the remaining liquid lava, helping to keep it hot and inviscid enough to continue flowing. The word ''lava'' comes from Italian and is probably derived from the Latin word ''labes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
