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Melanophlogite
Melanophlogite (MEP) is a rare silicate mineral and a polymorph of silica (SiO2). It has a zeolite-like porous structure which results in relatively low and not well-defined values of its density and refractive index. Melanophlogite often overgrows crystals of sulfur or calcite and typically contains a few percent of organic and sulfur compounds. Darkening of organics in melanophlogite upon heating is a possible origin of its name, which comes from the Greek for "black" and "to be burned". History Melanophlogite was identified and named by Arnold von Lasaulx in 1876 although G. Alessi had described a very similar mineral as early as in 1827. The mineral had a cubic crystal structure; chemical analysis revealed that it is mainly composed of SiO2, but also contains up to 12% of carbon and sulfur. It was suggested that the decomposition of organic matter (carbon) in the mineral was responsible for its blackening upon heating. All studied samples originated from Sicily, and thus th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicon Dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as a synthetic product. Notable examples include fused quartz, fumed silica, silica gel, opal and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries. Structure In the majority of silicates, the silicon atom shows tetrahedral coordination, with four oxygen atoms surrounding a central Si atomsee 3-D Unit Cell. Thus, SiO2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. In contrast, CO2 is a linear molecule. The starkly different structures of the dioxid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicate Minerals
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 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 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 earth. General structure A silicate mineral is general ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahydrothiophene
Tetrahydrothiophene is an organosulfur compound with the formula (CH2)4S. The molecule consists of a five-membered saturated ring with four methylene groups and a sulfur atom. It is the saturated analog of thiophene. It is a volatile, colorless liquid with an intensely unpleasant odor. It is also known as thiophane, thiolane, or THT. While THT is not particularly common, the vitamin biotin is essential for life in aerobic organisms. Synthesis and reactions Tetrahydrothiophene is prepared by the reaction of tetrahydrofuran with hydrogen sulfide. This vapor-phase reaction is catalyzed by alumina and other heterogenous acid catalysts. This compound is a ligand in coordination chemistry, an example being the complex chloro(tetrahydrothiophene)gold(I). Oxidation of THT gives the sulfone sulfolane, which is of interest as a polar, odorless solvent: : Sulfolane is, however, more conventionally prepared from butadiene. Natural occurrence Both unsubstituted and substituted tetra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pardubice Region
Pardubice Region ( cs, Pardubický kraj; , ; pl, Kraj pardubicki) is an administrative unit ( cs, kraj) of the Czech Republic, located mainly in the eastern part of its historical region of Bohemia, with a small part in northwestern Moravia. It is named after its capital Pardubice. As an administrative unit, Pardubice Region has existed three times in the course of history. It was established for the first time in 1850, and extended from Český Brod to the Bohemian-Moravian border. In its second existence, it was one of 19 regions as they were set between 1949 and 1960. After 1960, Pardubice became the capital of Pardubice district, which was part of the Eastern Bohemian Region (capital Hradec Králové). The Pardubice Region, as it is now, was reestablished in 2000. Administrative divisions The Pardubice Region is divided into 4 districts: There are a total of 451 municipalities in the region (as of 2019). Among these are 15 municipalities with extended powers and 26 munici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crimea
Crimea, crh, Къырым, Qırım, grc, Κιμμερία / Ταυρική, translit=Kimmería / Taurikḗ ( ) is a peninsula in Ukraine, on the northern coast of the Black Sea, that has been occupied by Russia since 2014. It has a population of 2.4 million. The peninsula is almost entirely surrounded by the Black Sea and the smaller Sea of Azov. The Isthmus of Perekop connects the peninsula to Kherson Oblast in mainland Ukraine. To the east, the Crimean Bridge, constructed in 2018, spans the Strait of Kerch, linking the peninsula with Krasnodar Krai in Russia. The Arabat Spit, located to the northeast, is a narrow strip of land that separates the Sivash lagoons from the Sea of Azov. Across the Black Sea to the west lies Romania and to the south is Turkey. Crimea (called the Tauric Peninsula until the early modern period) has historically been at the boundary between the classical world and the steppe. Greeks colonized its southern fringe and were absorbed by the Ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territories of the United States by population, most populous U.S. state and the List of U.S. states and territories by area, 3rd largest by area. It is also the most populated Administrative division, subnational entity in North America and the 34th most populous in the world. The Greater Los Angeles area and the San Francisco Bay Area are the nation's second and fifth most populous Statistical area (United States), urban regions respectively, with the former having more than 18.7million residents and the latter having over 9.6million. Sacramento, California, Sacramento is the state's capital, while Los Angeles is the List of largest California cities by population, most populous city in the state and the List of United States cities by population, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Province Of Livorno
The province of Livorno or, traditionally, province of Leghorn ( it, provincia di Livorno) is a province in the Tuscany region of Italy. It includes several islands of the Tuscan Archipelago, including Elba and Capraia. Its capital is the city of Livorno. When formed in 1861, the province included only Livorno and Elba Island. It was extended in 1925 with land from the provinces of Pisa and Genoa. It has an area of and a total population of 343,003 (2012). There are 19 ''comuni'' (singular: ''comune'') in the province. The coastline of the area is known as "Costa degli Etruschi" (Etruscan Coast). The province of Livorno is coastal and contains a number of coastal towns. Livorno is a highly important port for tourism and trading, and a number of watchtowers are located nearby the city. At Calafuria, the sea contains sponges, shellfish, fish, and protected red coral (''Corallium rubrum''). The coastlines of Quercianella and Castiglioncello are rocky. The waters around the province ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Province Of Caltanissetta
The Province of Caltanissetta ( it, provincia di Caltanissetta; scn, pruvincia di Nissa or ; officially ''Libero consorzio comunale di Caltanissetta'') is a province in the southern part of Sicily, Italy. Following the suppression of the Sicilian provinces, it was replaced in 2015 by the Free municipal consortium of Caltanissetta. It contains 22 ''comuni'', which are listed at Comuni of the Province of Caltanissetta. Its coat of arms is a red crest and two green leaf stems on top with a laurel leaf on the right and a crown in the middle. The River Salso is the main river of the province; it is long and originates in the province of Palermo, and it flows into the Mediterranean in this province at the end of the Gulf of Gela. Bordering provinces and metropolitan cities In counterclockwise order: * Province of Agrigento, west * Metropolitan City of Palermo, north-west * Province of Enna, north * Metropolitan City of Catania, north-east * Province of Ragusa, east Geography The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Province Of Turin
The former Province of Turin ( it, Provincia di Torino; pms, Provinsa ëd Turin; french: Province de Turin) was a province in the Piedmont region of Italy. Its capital was the city of Turin. The province existed until 31 December 2014, when it was replaced by the Metropolitan City of Turin. Geography It had an area of , and a total population of (30 June 2011). There were 316 ''comuni'' (municipalities) in the province – the most of any province in Italy. The second highest ''comuni'' are in the Province of Cuneo which has 250. Torino, the former capital of the province, and capital of the present day Metropolitan City of Turin, was the first national capital of unified Italy in 1861. Economy The most important export items from the Turin province are automobiles, machinery, and metal products. The province has commercial relations with Germany, France, Poland, Spain, United Kingdom, Romania and Czech Republic. A large quantity of import and export is carried with these n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Province Of Parma
The Province of Parma ( it, Provincia di Parma) is a province in the Emilia–Romagna region of Italy. Its largest town and capital is the city of Parma. It is made up of 47 ''comuni''. It has an area of and a total population of around 450,000. The province is bordered by the Province of Reggio Emilia to the east, the Piacenza to the west, Lombardy's provinces of Cremona and Mantova to the north and by Liguria's provinces of La Spezia and Genoa and Tuscany's Province of Massa and Carrara to the south. History In 1861, Italian provinces were established on the French republican model. Italian Fascism saw the end of elections in the Province of Parma in the 1920s until the end of the Second World War. Geography The province is divided into three zones from north to south: the ''pianura'' (plains), the ''collina'' (hills) and the ''montagna'' (mountains). The Po river acts as a boundary with the nearby province of Cremona in the plains. The main centres of the ''collina' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cristobalite
Cristobalite is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the quartz group, which also include coesite, tridymite and stishovite. It is named after Cerro San Cristóbal in Pachuca Municipality, Hidalgo, Mexico. It is used in dentistry as a component of alginate impression materials as well as for making models of teeth. Properties Metastability Cristobalite is stable only above 1470 °C, but can crystallize and persist metastably at lower temperatures. The persistence of cristobalite outside its thermodynamic stability range occurs because the transition from cristobalite to quartz or tridymite is "reconstructive", requiring the breaking up and reforming of the silica framework. These frameworks are composed of Si O4 tetrahedra in which every oxygen atom is shared with a neighbouring t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
