Showing papers on "Goethite published in 1969"

The mineralogy and geochemistry of a nickeliferous laterite profile (Greenvale, Queensland, Australia)

Abstract: A laterite profile on serpentinite at Greenvale, Australia, has been investigated in order to elucidate the formation of the secondary minerals and the trace element behaviour during tropical weathering. Mineralogical and chemical studies indicate that the serpentine alters to montmorillonite, aluminous goethite, and quartz. Chromiferous chlorite, a stable component, becomes concentrated in the weathering profile. No members of the kaolin group or bauxite group were identified, and the alumina occurs chiefly in solid solution with the goethite. In the upper levels of the profile serpentine and mont-morillonite disappear completely, and the amount of alumina substituting in the goethite increases. With increasing depth the Fe2O3 and Al2O3 content falls, whereas SiO2 and MgO increase. This is in accordance with the usual trends of lateritic weathering. The trace elements Ni, Co, Mn, Cu and Cr are all concentrated during the weathering process. Evidence suggests that Ni is associated with goethite, and possibly is incorporated in the lattice of this mineral. No appreciable nickel is associated with the manganese minerals. The concentration of Cr takes place mainly through the increase of the stable chromiferous chlorite.

Reactions of Triammonium Pyrophosphate with Soils and Soil Minerals1

Abstract: Whole soils of several genetic groups promoted hydrolysis of pyrophosphate to orthophosphate in dilute solutions, but the catalytic action was largely biological. Clay minerals and hydrous oxides, particularly iron oxide, showed some catalytic activity which might be significant in sterile, dilute pyrophosphate solutions. The microorganisms were inactive in solutions more concentrated than 0.2M in pyrophosphate. Autoclaved specimens of kaolinite, montmorillonite, and goethite suspended in sterile 0.5 or 2.0M solutions of (NH₄)₃-HP₂O₇ for 15 weeks were practically inert, but gibbsite dissolved slowly in both solutions and Al(NH₄)₂P₂O₇OH · 2H₂O began to crystallize from the 0.5M solution after 5 weeks. Less than 6% of the pyrophosphate in these solutions, with or without suspended mineral, was hydrolyzed in 15 weeks; only goethite increased the hydrolysis, and that barely significantly. Pyrophosphate was adsorbed more strongly on clays and soils than was orthophosphate.

Goethite-Hematite Stability Relations with Relevance to Sea Water and the Red Sea Brine System

Abstract: Goethite is the dominant Fe+3 bearing mineral in all cores from the Red Sea brine deposits with the exception of core station 84 within the Atlantis II Deep where hematite has been transformed from original goethite and limonite.

Magnetic Properties of Minerals from the Red Sea Thermal Brines

Abstract: Studies of the magnetic properties of sediment samples recovered from the thermal brine area of the Red Sea have been made. The minerals which have distinctive magnetic signatures, particularly on heating, are goethite, lepidocrocite, siderite, manganosiderite, pyrite, hematite and small quantities of a ferrimagnetic mineral, which is probably maghemite.

Minerology of Nipe Clay

Abstract: The mineralogy of Nipe clay was characterized by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), BET surface area, and chemical analysts. The major components of the clay fraction are goethite, gibbsite, hematite and kaolinite. Goethite is the predominant iron oxide as indicated by the high intensity of the XRD peaks. The unit cell dimensions of goethite, estimateod from the XRD data, were a = 4.603 A, b = 9.806 A and c = 3.002 A. The unit cell dimensions of hematite were a = 5.037 A, and c = 13.735 A. The extent of aluminum substitution in goethite and hematite was also estimated from the XRD data. The mole % Al in goethite, based on the d (111) value, was 15.57 mole percent, whereas when the a-dimension of the unit cell was used, a value of 12.86 mole percent was obtained. The estimated mole percent Al substitution in hematite was 0.67. The hematite/goethite ratio as estimated from the relative intensities of the 104 peak of hematite and the 110 peak of goethite was 0.51. Kaolinite showed a high capacity to absorb IR radiation as indicated by strong absorption peaks around 1000 and 3700 cm -1 . The surface area of the clay as determined by the BET method was 55.26 m 2 /g. The ratio of Fe ox /Fe d was very low (1.17x10 -2 ), indicating that the iron oxides occur in well crystallized form.