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Genesis and Morphology of Iron Sulfides in Gray Kaolins

Published online by Cambridge University Press:  02 April 2024

G. Norman White ,
J. B. Dixon ,
R. M. Weaver  and
A. C. Kunkle
G. Norman White
Affiliation:
Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas 77843
J. B. Dixon
Affiliation:
Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas 77843
R. M. Weaver
Affiliation:
J. M. Huber Corporation, Huber, Georgia 31298
A. C. Kunkle
Affiliation:
J. M. Huber Corporation, Huber, Georgia 31298
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Abstract

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Many of the presently oxidized Georgia kaolins probably existed originally in the reduced (gray) state. For that reason, the distribution of iron sulfides in presently gray kaolins may elucidate features observed in oxidized kaolins. An understanding of the nature of gray kaolins may also aid in the development of processing strategies for the exploitation of these abundant resources. The size, morphology, and degree of crystallite bonding of iron sulfides (pyrite and marcasite) in three gray kaolin cores from the Macon, Georgia kaolin district were examined by X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, and other physical and chemical methods. Pyrite and marcasite were identified as dominantly gravel- and sand-size equant crystals and crystal aggregates, rather than as framboids. Pyrite crystals commonly showed rough octahedral faces, which extended over minor cube faces. Locally, spiral growth dislocations were also observed. Marcasite was found in radiating, prismatic, and tabular crystals. In general, the marcasite crystal aggregates were much more fragile than those of pyrite. The dominance of octahedral crystal shapes and textures of the pyrite suggest inorganic precipitation from solutions supersaturated with respect to octahedral crystal faces.

Keywords

KaoliniteMarcasiteMorphologyOxidationPyriteScanning electron microscopySulfide
Type
Research Article
Information
Clays and Clay Minerals , Volume 39 , Issue 1 , February 1991 , pp. 70 - 76
Copyright
Copyright © 1991, The Clay Minerals Society

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