Showing papers on "Goethite published in 1971"

Transformation of hematite to goethite in soils.

Abstract: IN many parts of the world, especially in those that were not glaciated during the Pleistocene epoch, red hematitic soils that formed in a previous climate (different from the present one) still exist. In regions where the present climate is cooler and more humid than the previous one, the red colour seems to be disappearing and being replaced by more yellowish-brown colours that indicate the mineralogical transformation of hematite (α-Fe2O3) to goethite (α-FeOOH).

Jarosite-geoethite stabilities at 25 °C, 1 ATM

Abstract: Eh, pH and log activity diagrams were calculated to demonstrate the equilibrium relationships between jarosite-goethite-pyrite at 25 °C, 1 atm. Interpretation of these diagrams in light of natural occurrences of iron minerals in the oxidation zone of a sulfide deposit indicates that goethite (or hematite) is the stable mineral in the normal weathering environment. Jarosite is shown to be stable in an acid (pH<3) medium which is moderate to highly oxidizing (Eh-pH). It appears that the persistence of jarosite outside its stability field is due to the sluggishness of the reaction jarosite → goethite.

Electrostatic energy calculations of diaspore (α AlOOH), goethite (α FeOOH) and groutite (α MnOOH)

Abstract: befriedigen, die kleinste elektrostatische Energie aufweist ; x, y, z sind die Ladungen von AI, O und H. Berechnungen der elektrostatischen Energie nach dem Bom-Haber-Zyklus lassen erwarten, daß die Ladungen vollständig ionisierter Atome (< = 1) die besten Werte ergeben. Die Rechnung zeigte, daß auch im Goethit die H-Atome sich in der Nähe der Lagen minimaler elektrostatischer Energie befinden, wenn Fe, O und H als vollständig ionisiert angenommen werden. Diese Erfahrung wurde dazu benutzt , die Wasserstoff-Lage in der S t ruktur von Grouti t vorauszusagen.

Iron formation and supergene iron ores of the Goe range area, Liberia

Abstract: Two parallel beds of metamorphosed Precambrian iron formation located within the Goe Range area of the central coastal region of Liberia are described. These beds consist of itabirites and silicate iron formation. They are associated with schists and quartzites which are metamorphosed mature pelitic sediments and cherts. The chemistry of the iron formation is similar to that of other middle Precambrian iron formations except for higher phosphorous and aluminum content. Relative concentrations of Al and P tend to coincide in layers conformable with structure and bedding.Ore concentrations in which iron content reaches a maximum of 65% are described. Such concentrations are not generally formed over silicate rich horizons. Controls of ore localization are mineralogy, grain size, structure and width of iron formation. Leaching of quartz from iron formation by meteoric waters is associated with intermittent lateritization of surface zones. Lateritization has caused surface enrichment in alumina, and mobilization of iron. The 5-10 meter thickness of the alumina enriched goethite capping indicates the depth to which Eh and pH fluctuations are significant.Supergene waters remove quartz from iron formation, leaving a residual mass of soft or biscuit ores under the surface capping. The ores persist in the largest concentrations to depths of more than 100 meters.