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This article in SSSAJ

  1. Vol. 52 No. 1, p. 288-291
     
    Received: Feb 19, 1987


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doi:10.2136/sssaj1988.03615995005200010052x

Goethite and Hematite Formation in the Presence of Clay Minerals and Gibbsite at 25°C

  1. U. Schwertmann 
  1. Lehrstuhl für Bodenkunde, Technische Universität München, 8050 Freising-Weihenstephan, Federal Republic of Germany

Abstract

Abstract

After 8.4 yr at 25 °C under water, ferrihydrite was almost completely converted into a mixture of goethite and hematite. In contrast, aging in the presence of various clay minerals and gibbsite retarded (kaolinite, illite, smectite, gibbsite) or even blocked (soil smectite, allophane) transformation. The conversion rate was inversely related to the final Si concentration in solution. In addition, the presence of clay minerals resulted in higher hematite to goethite ratios, lower mean crystallite dimensions for both oxides, and the incorporation of Al into the goethite and hematite structures. Similar effects have been observed for coexisting goethite and hematite in soils.

Contribution from Lehrstuhl für Bodenkunde, Technische Universität München, Freising-Weihenstephan, FRG.

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