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Reduction of Fe(III) in griffithite

P. Komadel, J. Madejova, D. A. Laird, Y. Xia and J. W. Stucki
Reduction of Fe(III) in griffithite
Clay Minerals (September 2000) 35 (4): 625-634


Griffithite is a trioctahedral smectite with dioctahedral domains, found in the <2 mu m fraction of weathered basic rock from Griffith Park, California, USA. Crystalline admixtures (albite, calcite, quartz and maghemite) are concentrated in the 0.2-2 mu m fraction, while the <0.06 mu m fraction contains only trace amounts of other minerals. Griffithite is primarily an Fe-rich saponite with negative charge located in the tetrahedral sheets. The octahedral occupancy is approximately 91%, and approximately 26% of the octahedra contain trivalent atoms imparting a net positive charge to the octahedral sheet. Medium levels of Fe(III) reduction in griffithite, up to 60% of total Fe, can be achieved by adding solid sodium dithionite to clay dispersions in a citrate-bicarbonate buffer. By contrast >90% reduction of Fe(III) to Fe(II) is achieved in nontronites using the same method. The lower reducibility of Fe(III) in griffithite relative to nontronites may be due to structural differences between griffithite and nontronites, such as a more negative tetrahedral charge and a positive octahedral charge.

ISSN: 0009-8558
EISSN: 1471-8030
Serial Title: Clay Minerals
Serial Volume: 35
Serial Issue: 4
Title: Reduction of Fe(III) in griffithite
Affiliation: Slovak Academy of Sciences, Institute of Inorganic Chemistry, Bratislava, Slovakia
Pages: 625-634
Published: 200009
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 26
Accession Number: 2001-064942
Categories: Mineralogy of silicatesSoils
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Secondary Affiliation: U. S. Department of Agriculture, USA, United StatesUniversity of Illinois, USA, United States
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200120
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