W. F. Bradley

Bio: W. F. Bradley is an academic researcher from Urbana University. The author has contributed to research in topics: Clay minerals & Montmorillonite. The author has an hindex of 17, co-authored 24 publications receiving 1761 citations.

The structural scheme of attapulgite

Abstract: The name attapulgite was applied in 1935 by J. De Lapparentl to a clay mineral which he encountered in fuller's earths from Attapulgus, Georgia, and Mormoiron, France. Objections have been raised, and these objections were recently reviewed by De Lapparent,2 that the material involved does not justify the application of a mineral name. However, no attempt has been made to study the crystal structure. De Lapparent himself has suggested for classification purposes that attapulgite is a layer sil icate related to the micas, but some obvious inconsistencies with the o-ray powder diffraction patterns of the mineral have suggested the desirabil ity of attempting a better explanation. The material used in this investigation was obtained from the Attapulgus Clay Co., Attapulgus, Ga. The raw clay was dispersed and freed of large crystall ine impurit ies by sedimentation. Centrifuge fractions were then obtained, of which particularly the fraction between.1 and.05i/ appeared homo-

Quantitative Estimations of Clay Minerals by Diffraction Methods

Abstract: The clay mineral components of Recent sediments and soil materials exhibit structural attributes unlike those of many so-called standard clay materials. The interpretation and significance of some of these is discussed in detail. Factors involved in analyzing these materials quantitatively are considered and a general procedure outlined.

Investigation of the effect of heat on the clay minerals illite and montmorillonite

Abstract: Samples of three purified illites, one purified montmorillonite, and one natural clay containing montmorillonite, quartz, and limonite were heated at successive temperatures up to 1400°C. X-ray and optical determinations were made on all samples. The changes that take place in the clay minerals, illite and montmorillonite, when they are heated at various temperatures up to 1400°C. are discussed.

Mineralogy and Sedimentation of Recent Deep-Sea Clay in the Atlantic Ocean and Adjacent Seas and Oceans

Abstract: Semiquantitative mineral analysis has been done by X-ray diffraction on the < 2 μ- and 2–20 μ-size fractions of approximately five hundred Recent deep-sea core samples from the Atlantic, Antarctic, western Indian Oceans, and adjacent seas. Relative abundances of montmorillonite, illite, kaolinite, chlorite, gibbsite, quartz, amphibole, clinoptilolite-heulandite(?), and pyrophyllite(?) were determined. Mixed-layer clay minerals, feldspars, and dolomite were also observed but not quantitatively evaluated. From the patterns of mineral distribution, the following conclusions appear warranted: Most Recent Atlantic Ocean deep-sea clay is detritus from the continents. The formation of minerals in situ on the ocean bottom is relatively unimportant in the Atlantic but may be significant in parts of the southwestern Indian Ocean. Mineralogical analysis of the fine fraction of Atlantic Ocean deep-sea sediments is a useful indicator of sediment provenance. Kaolinite, gibbsite, pyrophyllite, mixed-layer minerals, and chlorite contribute the most unequivocal provenance information because they have relatively restricted loci of continental origin. Topographic control over mineral distribution by the Mid-Atlantic Ridge in the North Atlantic Ocean precludes significant eolian transport by the jet stream and emphasizes the importance of transport to and within that part of the deep-sea by processes operative at or near the sediment-water interface. Transport of continent-derived sediment to the equatorial Atlantic is primarily by rivers draining from South America and by rivers and wind from Africa. The higher proportion of kaolinite and gibbsite in deep-sea sediments adjacent to small tropical South American rivers reflects a greater intensity of lateritic weathering than is observed near the mouths of the larger rivers. This may be explained by a greater variety of pedogenic conditions in the larger drainage basins, resulting in an assemblage with proportionately less lateritic material in the detritus transported by the larger rivers despite their quantitatively greater influence on deep-sea sediment accumulation. In the South Atlantic Ocean, the fine-fraction mineral assemblage of surface sediment in the Argentine Basin is sufficiently unlike that adjacent to the mouth of the Rio de la Plata to preclude it as a major Recent sediment source for that basin. The southern Argentine Continental Shelf, the Scotia Ridge, and the Weddell Sea arc mineralogically more likely immediate sources. Transport from the Weddell Sea by the Antarctic Bottom Water may be responsible for the northward transport of fine-fraction sediment along parts of the western South Atlantic as far north as the Equator.

Halloysite clay minerals — a review

Abstract: Halloysite clay minerals are ubiquitous in soils and weathered rocks where they occur in a variety of particle shapes and hydration states. Diversity also characterizes their chemical composition, cation exchange capacity and potassium selectivity. This review summarizes the extensive but scattered literature on halloysite, from its natural occurrence, through its crystal structure, chemical and morphological diversity, to its reactivity toward organic compounds, ions and salts, involving the various methods of differentiating halloysite from kaolinite. No unique test seems to be ideal to distinguish these 1:1 clay minerals, especially in soils. The occurrence of 2:1 phyllosilicate contaminants appears, so far, to provide the best explanation for the high charge and potassium selectivity of halloysite. Yet, hydration properties of the mineral probably play a major role in ion sorption. Clear trends seem to relate particle morphology and structural Fe. However, future work is required to understand the possible mechanisms linking chemical, morphological, hydration and charge properties of halloysite.

Quantitative interpretation of mineralogical composition from X-ray and chemical data for the Pierre Shale

Abstract: -----------------------------------------Introduction.-------------------------------------X-ray analysis ________ --_--_--_----_________ ------Sample preparation and treatment _______________ _ Interpretation---------------------------------Whole rock data ___________________________ _ Carbonate minerals.--------_____ -----_ Disordered cristobalite _________________ _ Total clay minerals __ -------__________ _ Clay fraction data_------------__ ------__ _ Clay minerals present __ ----------------Comparison of X-ray peak sizes _________ _ Estimation of kaolinite and chlorite ______ _ Examples of interpretation __________________ _ ReproducibilitY------------------------------------Long-term reproducibility----__________________ _ Accuracy-comparison with chemical analyses _________ _ Sulfide, sulfate, and carbonate minerals ___________ _ Page

Selective sorption and fixation of cations by clay minerals : A review

Abstract: Investigations concerning selective sorption and fixation of K and similar cations by clay minerals and soil clays and the mechanisms of these reactions are reviewed. In particular, recent observations on selective sorption of these ions in dilute solutions by weathered micas and vermiculite in relation to the interlayer structures are discussed in detail. Also, implications of the resistance to weathering of small mica particles to cation selectivity by soils are described. Despite the increased understanding of sorption and fixation reactions, the following aspects remain unclear. First, the mechanism of the collapse of alternate layers in vermiculite on K or Cs sorption has not been unequivocally established. Second, factors that impart stability to the central core of mica particles so that K extraction becomes progressively difficult are not known. Third, inability of Ca or Mg ions to expand interlayers of Cs-saturated vermiculite in contrast to K-saturated vermiculite is not completely understood.