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hematite
(Encyclopedia)hematite hĕmˈətīt [key], mineral, an oxide of iron, Fe2O3, containing about 70% metal, occurring in nature in red to reddish-brown earthy masses and in steel-gray to black crystalline forms. Hemat...brown hematite
(Encyclopedia)brown hematite: see limonite.limonite
(Encyclopedia)limonite hĕmˈətīt, hēˈ– [key], yellowish to dark brown mineral, a hydrated oxide of iron, FeO(OH)·nH2O, occurring commonly in deposits of secondary origin, i.e., those formed by the alteratio...ocher
(Encyclopedia)ocher ōˈkər [key], mixture of varying proportions of iron oxide and clay, used as a pigment. It occurs naturally as yellow ocher (yellow or yellow-brown in color), the iron oxide being limonite, or...Mesabi
(Encyclopedia)Mesabi məsäbˈē [key], range of low hills, NE Minn., once famous for its extensive iron ore deposits. The ores were found in a belt c.110 mi (180 km) long and from 1 to 3 mi (1.6–4.8 km) wide bet...corundum
(Encyclopedia)corundum kərŭnˈdəm [key], mineral, aluminum oxide, Al2O3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal system and in mass...quartz
(Encyclopedia)quartz, one of the commonest of all rock-forming minerals and one of the most important constituents of the earth's crust. Chemically, it is silicon dioxide, SiO2. It occurs in crystals of the hexagon...iron
(Encyclopedia)iron, metallic chemical element; symbol Fe [Lat. ferrum]; at. no. 26; at. wt. 55.845; m.p. about 1,535℃; b.p. about 2,750℃; sp. gr. 7.87 at 20℃; valence +2, +3, +4, or +6. Iron is biologically s...Aswan
(Encyclopedia)Aswan or Assuan both: äswänˈ, ăswănˈ [key], city (1986 pop. 190,579), capital of Aswan governorate, S Egypt, on the Nile River at the First Cataract. It is one of the driest cities in the world....Browse by Subject
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