Ferruginous vernadite in an Indian Ocean ferromanganese nodule

Abstract

Select area electron diffraction and microanalysis of the optically dark component of a ferromanganese nodule from the South East Indian Ocean Manganese Field indicate that this is composed of a random stratification of crystallites of vernadite MnO2. (R2O, RO, R2O3)x. yH2O, where R represents elements such as K, Ba, Na, Ca, Mg, and a disordered hydrated iron oxide, possibly ferrihydrite 5Fe2, O3. 9H2O or feroxyhyte δ′-FeOOH. Whether the dark component is an irregular mixed-layer hybrid mineral or a layered accumulation resulting from epitaxy of the above phases is uncertain.

Natural speciation of Mn, Ni, and Zn at the micrometer scale in a clayey paddy soil using X-ray fluorescence, absorption, and diffraction

“…In these areas, the fine matrix is cemented by turbostratic birnessite and poorly crystalline ferric (oxyhydr)oxides (FeOx) which give rise to broad scattering bands at ~2.2 Å and ~1.7 Å in the XRD patterns. This Fe-Mn oxide association, generally referred to as Fe-rich vernadite (Fevernadite) and Mn-bearing feroxyhite (Mn-feroxyhite) (Manceau and Combes, 1988;Manceau et al, 1992;Ostwald, 1984a;Varentsov et al, 1991), is common in soils, such as those from the Moscow plain (Vodyanitskii et al, 2002). Minor lepidocrocite and goethite were also identified in the clayey matrix, consistent with the XRD texture analysis.…”

Formation of todorokite from vernadite in Ni-rich hemipelagic sediments

“…Despite the lack of direct evidence, todorokite has long been suspected to form from vernadite (Burns and Burns, 1978b). Three varieties of vernadite can be distinguished on the basis on chemical and diffraction data: 7Å -vernadite, 10Å -vernadite, and Fe-vernadite (Ostwald, 1984;Varentsov et al, 1991;Manceau et al, 2007a,b). The first two varieties are one-water layer (7Å ) and two-water layer (10Å ) hydrates of the same type of mineral, each of which consists of octahedral Mn layers stacked vertically with a constant separation, but without three-dimensional (3D) periodicity.…”

Hollandite in Hawaiian basalt: a relocation site for weathering-mobilized elements

“…Based on the relatively high Fe/Mn ratio, it is ferruginous vernadite, a Mn-oxide commonly observed in a marine environment (Ostwald, 1984;Bolten et al, 1988). The structure of vernadite is not fully understood and, according to Manceau et al (1992), vernadite is probably a hybrid between phyllo-and tectomanganate.…”