sulfate mineral

sulfate also spelled  Sulphate,  

       Sulfate minerals Sulfate mineralsany naturally occurring salt of sulfuric acid. About 200 distinct kinds of sulfates are recorded in mineralogical literature, but most of them are of rare and local occurrence. Abundant deposits of sulfate minerals, such as barite and celestite, are exploited for the preparation of metal salts. Many beds of sulfate minerals are mined for fertilizer and salt preparations, and beds of pure gypsum are mined for the preparation of plaster of paris.

      All sulfates possess an atomic structure based on discrete insular sulfate (SO42-) tetrahedra, i.e., ions in which four oxygen atoms are symmetrically distributed at the corners of a tetrahedron with the sulfur atom in the centre. These tetrahedral groups do not polymerize, and the sulfate group behaves as a single negatively charged molecule, or complex. Thus, sulfates are distinct from the silicates and borates, which link together into chains, rings, sheets, or frameworks.

      Sulfate minerals can be found in at least four kinds: as late oxidation products of preexisting sulfide ores, as evaporite deposits, in circulatory solutions, and in deposits formed by hot water or volcanic gases. Many sulfate minerals occur as basic hydrates of iron, cobalt, nickel, zinc, and copper at or near the source of preexisting primary sulfides. The sulfide minerals, through exposure to weathering and circulating water, have undergone oxidation in which the sulfide ion is converted to sulfate and the metal ion also is changed to some higher valence state. Noteworthy beds of such oxidation products occur in desert regions, such as Chuquicamata, Chile, where brightly coloured basic copper and ferric iron sulfates have accumulated. The sulfate anions generated by oxidation processes may also react with calcium carbonate rocks to form gypsum, CaSO4·2H2O. Sulfates formed by the oxidation of primary sulfides include antlerite [Cu3(SO4)(OH)4], brochantite [Cu4(SO4)(OH)6], chalcanthite [Cu2+(SO4)·5Η2Ο], anglesite (PbSO4), and plumbojarosite [PbFe3+6(SO4)4(OH)12].

      Soluble alkali and alkaline-earth sulfates crystallize upon evaporation of sulfate-rich brines (brine) and trapped oceanic salt solutions. Such brines can form economically important deposits of sulfate, halide, and borate minerals in thick parallel beds, as the potash deposits at Stassfurt, Ger., and the southwestern United States. Many of the sulfate minerals are salts of more than one metal, such as polyhalite, which is a combination of potassium, calcium, and magnesium sulfates.

      Sulfate minerals common in evaporite deposits include anhydrite, gypsum, thenardite (Na2SO4), epsomite (MgSO4·7H2O), glauberite [Na2Ca(SO4)2], kainite (MgSO4·KCl·3H2O), kieserite (MgSO4·H2O), mirabilite (Na2SO4·10H2O), and polyhalite [K2Ca2Mg(SO4)4·2H2O].

      Groundwater carrying sulfate anions reacts with calcium ions in muds, clays, and limestones to form beds of gypsum. The massive material is called alabaster or plaster of paris (originally found in the clays and muds of the Paris basin). If such beds become deeply buried or metamorphosed (altered by heat and pressure), anhydrite may form by dehydration of the gypsum.

      Numerous sulfates, usually simple, are formed directly from hot aqueous solutions associated with fumarolic (volcanic gas) vents and late-stage fissure systems in ore deposits. Noteworthy examples include anhydrite, barite, and celestine.

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Universalium. 2010.

Look at other dictionaries:

  • sulfate — [ sylfat ] n. m. • 1787; de sulf(o) et suff. chim. ate ♦ Sel ou ester de l acide sulfurique. ⇒vx couperose, vitriol. Sulfates acides. ⇒ bisulfate. Sulfates et persulfates. Sulfates naturels de plomb, de calcium hydraté. ⇒ gypse. Sulfate de cuivre …   Encyclopédie Universelle

  • sulfaté — sulfate [ sylfat ] n. m. • 1787; de sulf(o) et suff. chim. ate ♦ Sel ou ester de l acide sulfurique. ⇒vx couperose, vitriol. Sulfates acides. ⇒ bisulfate. Sulfates et persulfates. Sulfates naturels de plomb, de calcium hydraté. ⇒ gypse. Sulfate… …   Encyclopédie Universelle

  • Sulfate de cuivre — cristal de sulfate de cuivre hydraté Général Nom IUPAC Sulfate de cuivre (II) …   Wikipédia en Français

  • Sulfate cuprique — Sulfate de cuivre Sulfate de cuivre cristal de sulfate de cuivre hydraté Général Nom IUPAC Sulfate de cuivre (II) …   Wikipédia en Français

  • Sulfate de Cuivre — cristal de sulfate de cuivre hydraté Général Nom IUPAC Sulfate de cuivre (II) …   Wikipédia en Français

  • Sulfate de cuivre(II) — Sulfate de cuivre Sulfate de cuivre cristal de sulfate de cuivre hydraté Général Nom IUPAC Sulfate de cuivre (II) …   Wikipédia en Français

  • Sulfate de cuivre pentahydraté — Sulfate de cuivre Sulfate de cuivre cristal de sulfate de cuivre hydraté Général Nom IUPAC Sulfate de cuivre (II) …   Wikipédia en Français

  • Sulfate d'ammonium — Structure du sulfate d ammonium …   Wikipédia en Français

  • Sulfate de calcium — Général Nom IUPAC sulfate de calcium Synonymes …   Wikipédia en Français

  • Mineral — Mineral, ein fester oder flüssiger, einheitlicher, d.h. nach seinen chemischen und physikalischen Eigenschaften in jedem Teilchen gleichmäßiger Naturkörper von einer bestimmten, in einer Formel ausdrückbaren chemischen Zusammensetzung. Künstliche …   Lexikon der gesamten Technik

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