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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 the presence of vermiculite, the ion product (Al)(OH)3 in solution was maintained at 10-33∙0 and no gibbsite was formed with time as mentioned in this paper.
Abstract: A specimen of Kenya vermiculite contained no mica or chlorite layers either as separate phases or as components of an interstratifled structure. Dehydroxylation occurred in two stages, at 550° and 850°C, with approximately equal amounts of hydroxyl liberated in each stage. Al-saturated Kenya vermiculite showed low temperature dehydration characteristics similar to those of the natural Mg-saturated specimen, but the DTA, TGA and oscillating-heating X-ray diffraction patterns showed that the three stage dehydration process was not as clear-cut with the Al-saturated specimen. As with montmorillonite, when small amounts of aluminum were precipitated by the addition of Ca(OH)2 in the presence of vermiculite, the Al(OH)x, was taken up and held indefinitely by the clay, the ion product (Al)(OH)3 in solution was maintained at 10-33∙0 and no gibbsite was formed with time. With large amounts, 800 and 1600 me Al(OH)x per 100g vermiculite, the hydroxide was held initially in the interlayer space, but gibbsite was eventually formed as (Al)(OH)3 approached the solubility product of gibbsite. Unlike montmorillonite, the vermiculite specimens retained an appreciable amount of the interlayer hydroxide and did not regain the original C.E.C. values as gibbsite was formed. Al-vermiculite which was repeatedly suspended in AlCl3 with (Al)(OH)3 maintained at a value less than 10-33∙8 liberated 435 me Mg, took up 208 me Al as an interlayer hydroxide and caused a reduction in C.E.C. from 130 to 28 me per 100g clay. With vermiculite an appreciable amount of the interlayer Al(OH)x was stable with respect to gibbsite whereas with montmorillonite it was not.
9 citations
TL;DR: In this article, the chemical composition of nine samples of Lower and Middle Chalk from the Givendale area of Yorkshire was determined; acetic acid residues were mechanically, chemically and mineralogically analysed.
Abstract: A B S T R A C T: The chemical composition of nine samples of Lower and Middle Chalk from the Givendale area of Yorkshire was determined; acetic acid residues were mechanically, chemically and mineralogically analysed. All nine chalk samples proved to be exceptionally pure calcium carbonate (96 _+ 1 '5~o), with only small amounts of MgO (1-03 _+ 0"53~o), A1202 (0.33_+0'28~o) and Fe202 (0'20 _+ 0'14~oo). Insoluble residues ranged from 1.07 to 4'46~o. Clay formed 56--88~o of the insoluble residue. The non-clay fraction consisted of flint, quartz, collophane, limonite, feldspar, tourmaline and zircon. The clay fractions were dominated by montmorillonite (50~o) with secondary illite (30~o), apatite (3~o), and quartz (8-30~oo). Kaolinite was detected by X-ray diffraction in the Lower Chalk. As part of a geochemical study of groundwater in Lower and Middle Chalk (Pitman, 1977a, b), data was required on the chemical and mineralogical properties of the chalk underlying an experimental catchement at Givendale, East Yorkshire. The most comprehensive work on the insoluble residues from chalk to date has been that of Weir & Catt (1965) who examined the mineralogy of the clay, silt and sand sized fractions from Upper Chalk, identifying montmorillonite, mica, quartz and apatite as being the dominant minerals, and analysed the chemistry of the clay fraction. Young (1965) examined residues from the Upper, Middle and Lower Chalk, and showed that whilst the clay residues from the Upper and Middle Chalk were illite/smectite, with trace amounts of apatite, those from the Lower Chalk were far more variable, containing illite, smectite, kaolinite, apatite and a mixed layer mineral (chlorite-vermiculite), confirming the earlier finds of Perrin 0956, 1957, 1964). Jeans 0968) reviewed in detail the clay mineralogy of the Lower Chalk, identified four characteristic assemblages, and showed that Yorkshire samples were characterized by a montmorillionite-illite ratio between 0.75 and 2.0 with little kaolinite, chlorite or vermiculite, and quartz generally exceeding 20~o. For the present study, samples of chalk were collected from the stratigraphic positions given below, using the nomenclature of Wright & Wright (1942) and Hill's (1888) section at Leavening; the estimated thickness of the Lower Chalk at Givendale is 20 m.
9 citations
TL;DR: The coalgate bentonite was formed by the alteration of cryptocrystalline basaltic ash erupted in Upper Miocene to Pliocene times and deposited in a freshwater lake on a land surface of earlier tholeiitic flows.
Abstract: The Coalgate Bentonite deposit has been formed by the alteration of cryptocrystalline basaltic ash erupted in Upper Miocene to Pliocene times and deposited in a freshwater lake on a land surface of earlier tholeiitic flows. Physical and chemical analysis shows the bentonite to consist essentially of non-swelling (Ca 2+ and Mg 2+) ferriferous-beidellite with minor ferriferous montmorillonite. The process of montmorillonitization probably involved a crystal chemical structural reorganization g ithout solution or precipitation and occurred in a mildly alkaline environment in which initial reducing conditions become oxidizing.
8 citations
17 Apr 1975
TL;DR: The most ubiquitous silicate minerals in soils throughout the world are the layer silicates known as the kaolin minerals as discussed by the authors, which include the dioctahedral minerals kaolinite, halloysite, dickite, and nacrite, and the three-dimensional minerals chrysotile, antigorite, chamosite and cronstedite.
Abstract: Probably the most ubiquitous silicate minerals in soils throughout the world are the layer silicates known as the kaolin minerals. The group includes the dioctahedral minerals kaolinite, halloysite, dickite, and nacrite, and the trioctahedral minerals chrysotile, antigorite, chamosite, and cronstedite. Halloysite and disordered forms of kaolinite seem to be the only members of the group formed in soils. The other minerals are formed hydrothermally or by regional metamorphism. They occur in soils, or could occur theoretically if they have not yet been found, as residual minerals inherited from hydrothermally or metamorphically formed deposits upon which soils have formed.
8 citations