Although Thermal Analysis is a useful technique in characterizing the clay constituent of a potentially valuable clay deposit, it is, perhaps, even more useful when the type and amount of non-clay impurities are important factors in its commercial appraisal. The effect of impurities on the physical and chemical properties of the clay may determine its potential uses in bulk, or it may be advisable to remove the impurity, either to improve the grade and quality of the clay or to provide a useful by-product. The application of both qualitative and quantitative thermal data, in the analysis and control of laboratory work in this field, is demonstrated by its use in the assessment of materials such as evaporite-rich clays, siliceous clays, and high-alumina clays.
Abstract Although seldom appreciated, the hydrocyclone offers several advantages over the more commonly used sedimentation/decantation method for clay separation. Large amounts of relatively concentrated clay suspensions may be separated in a matter of minutes. In addition, no dispersing agents are required and the shear conditions encountered by the suspension during passage through the hydrocyclone lead to particle disaggregation both in the silt and sub-micron size range. Formulae relating design factors of the hydrocyclone to separation performance exist but are of limited value as they are unable to predict the maximum particle size of the clay product or percentage recovery of any particular size of particle. Such data, determined from practical trials, are given for kaolinite, smectite and mixed-assemblage clay suspensions. Design limitations prevent the effective separation of clay products with ‘cut-off’ sizes finer than 5 µ m.
In addition to the commonly accepted format of the geological map, displaying lithological, stratigraphical and structural parameters, the British Geological Survey produces a range of thematic maps dealing with geophysical, geochemical and geotechnical data and providing information on mineral deposits, water supply and energy resources. Compilation scale varies with the level of detail to be displayed but only the smaller and intermediate scale maps are printed, in colour, as formal publications. Much of the larger scale work, incorporating more local detail, is produced for reference purposes and may be inspected in the Survey's map collections, although one-off copies can be produced on demand and, in the past, many of the older 'County' series six-inch maps were issued as printed sheets, especially for the coalfield areas. An outline is given of the variety of products that have been prepared by the Survey and of their relative availability as sales stock or reference copies.
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Abstract The plastic properties of clays are sufficiently variable to offer a simple but practical aid to identification. This can be done by using their Atterberg 'plastic limit' and 'plasticity index' values as parameters for an identification chart. The advantages and disadvantages of the technique are discussed, and results for a wide variety of clay minerals, particularly industrial clay types, are illustrated. A brief summary is also given of the effect of non-clay impurities, and reference is made to the correlation of Atterberg limit values with other physical properties of clays.
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