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brown hematite:see limonitelimonite
or brown hematite
, 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 alteration of minerals containing iron.
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an iron ore consisting of a natural agglomeration of hydroxides of iron (goethite, hydro-goethite, lepidocrocite, and other hydroxides) mixed with oxides and hydroxides of silicon and aluminum. Brown hematite is a finely dispersed mixture of minerals, ranging in color from dark-brown to light-yellow. It is observed in the form of friable ocherous masses, oolites, bean ore, concretions, and stalactites. It sometimes displaces pyrite, marcasite, and other iron-bearing sulfides, carbonates, and oxides and the organic mineral remains.
Brown hematite is one of the most widely distributed iron ores, having industrial value when it contains more than 30 per cent iron and a sufficiently small percentage of harmful admixtures—sulfur, phosphorus, and arsenic. Formation of brown hematite is due to oxidation processes in the surface zone of the earth’s crust. It is widely used in the metallurgical industry. The most important deposits of brown hematite are sedimentary (sea, river, lake, and marsh) and erosion crusts of ultrabasic rocks. The largest sedimentary oolite deposits of brown hematite are in the Western Siberian basin, Lisakovsk, Aiat, and Kerch, of the USSR, and in the Lotharingian area of France. Naturally alloyed brown hematite deposits of the erosion crust of ultrabasic rocks (with admixtures of nickel, chromium, and cobalt), which serve as the raw material for smelting of chrome-nickel steels and crude iron, are found in the USSR in the Urals (Khalilovo, Serov, and other locations), in Cuba (Mayari), and in New Caledonia.