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The x-ray identification and crystal structures of clay minerals
01 Jan 1961-
About: The article was published on 1961-01-01 and is currently open access. It has received 966 citations till now. The article focuses on the topics: Clay minerals.
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TL;DR: In this paper, the results of a 2eSj NMR study of the 2: 1 magnesium ribbon silicates, sepiolite and palygorskite are presented.
Abstract: The results of a 2eSj NMR study of the 2: 1 magnesium ribbon silicates, sepiolite and palygorskite are presented. Separate resonanoes between -92and -98 ppm for the three and two types, respectively, of silica units across the ribbons are obscrved. This provides infor-mation on factors other than tetrahedral aluminium substitution which can affect the Q3 chemical shift. Also observed is a Q2 SiOH resonance from crystal defects or edges. The structural changes which occur at the various stages of dehydration have been studied. Finally, some interesting observations on 2eSi rclaxation and cross-polatization dynamics are presented.
52 citations
TL;DR: In this paper, the structural transformations of high-temperature muscovite were determined using powder X-ray and neutron diffraction data collected at room temperature from preliminary heated and quenched samples at 650, 980, and 1095°C.
51 citations
TL;DR: Oxidation of octahedral ferrous to ferric iron in soil vermiculite clays and biotites increases the potassium-fixation capacity of vermicULites and increases the difficulty of replacing interlayer potassium in biotite.
Abstract: Oxidation of octahedral ferrous to ferric iron in soil vermiculite clays and biotites increases the potassium-fixation capacity of vermiculites and increases the difficulty of replacing interlayer potassium in biotites. This unexpected effect is believed to be related to an increase in the attractive forces between potassium ions and oxygen ions of the surface layers which is brought about by a tilting of the dipole of the octahedral hydroxyl ions from a perpendicular position to an inclined position with respect to the cleavage plane.
51 citations
TL;DR: In this paper, chemical and structural data on sepiolite-falcondoite in garnierite veins from the Falcondo Ni-laterite deposits, central Dominican Republic, are reported.
Abstract: New chemical and structural data on sepiolite-falcondoite in garnierite veins from the Falcondo Ni-laterite deposits, central Dominican Republic, are reported. Samples of Ni-sepiolite-falcondoite vary in colour from whitish green to green depending on the NiO content (wt.%) and the amount of silica present. The texture is normally schistose and friable but samples with considerable quartz and/or amorphous silica are compact and hard. Back-scattered electron images indicate that the samples are composed of at least three generations of Ni-sepiolite-falcondoite. The extreme refined cell parameters for Ni-sepiolite-falcondoite vary from 13.400(2), 27.006(4), 5.273(1) A to 13.340(3), 27.001(6), 5.267(1) A (space group Pncn). As the Ni content increases there is a small reduction in the a parameter. Chemical compositions determined by electron probe microanalysis cover a large interval of the Ni-sepiolite-falcondoite solid solution (Fal 3 and Fal 77 ). Individual samples show a considerable range in composition with the widest range determined in one sample from 4.63 to 22.40 wt.% NiO.
51 citations
TL;DR: A 14-A mineral coexisting with kaolin minerals, mica, and gibbsite in a Korean Ultisol and showing X-ray powder diffraction features of “chloritized” vermiculite was studied by a combination of methods as discussed by the authors.
Abstract: A 14-A mineral coexisting with kaolin minerals, mica, and gibbsite in a Korean Ultisol and showing X-ray powder diffraction features of “chloritized” vermiculite was studied by a combination of methods The 14-A mineral collapsed on saturation with K+ after extraction with hot 1/3 M sodium citrate, but the Si/Al ratio of the extracted material was close to 10 and kaolin minerals dissolved, as indicated by difference infrared spectroscopy The 14-A mineral was also collapsed by heating at or above 350°C The difference infrared spectra and the X-ray powder diffraction patterns indicated that two forms of kaolin mineral are present that differ in thermal stability; one decomposed by heating at or below 375°C and the other by heating above 375°C The former kaolin mineral is probably associated with vermiculite and the latter is present as a discrete form The 14-A mineral was inferred to be an intergradient vermiculite-kaolin mineral, in which most vermiculite layers each partially transform into double kaolin layers, and to represent an intermediate phase during the transformation of 2:1 to 1:1 layer silicates in acid soils
51 citations