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Transformation products of submicron-sized aluminum-substituted magnetite: Color and reductant solubilityMagnetite, when present as fine particles, is soluble in acid ammonium oxalate (pH equals 3). However, the commonly used extractant for free iron oxides (i.e., citrate dithionite-bicarbonate (CDB) is not very effective in dissolving magnetite in soils and geologic materials. Upon oxidation, magnetite transforms to maghemite; at elevated temperatures, maghemite inverts to hematite. This transformation causes a change in color from black to red and may affect the reductant solubility as well. The objectives here were to examine the color and reflectance spectral characteristics of products during the transformation of magnetite to maghemite to hematite and to study the effect of Al-substitution in magnetite on the above process. Reductant solubility of Al-substituted magnetite, maghemite, and hematite was also studied. In summary, the transformation of magnetite to maghemite was accompanied by a change in color from black to red because of the oxidation of Fe2(+) to Fe3(+). The phase change maghemite to hematite had a relatively minor effect on the color and the reflectance spectra.
Document ID
19920001033
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Golden, D. C.
(NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Ming, D. W.
(NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Lauer, H. V., Jr.
(Lockheed Engineering and Sciences Co. Houston, TX., United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1991
Publication Information
Publication: Program and Abstracts for Clay Minerals Society 28th Annual Meeting
Subject Category
Lunar And Planetary Exploration
Accession Number
92N10251
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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