Advances in the characterization of industrial minerals
The use of minerals by man is as old as the human race. In fact the advancement of human civilization has been intimately associated with the exploitation of raw materials. It is not by chance that the distinction of the main historical eras is based on the type of raw materials used. Hence the passage from the Paleolithic and Neolithic Age to the Bronze Age is characterized by the introduction of basic metals, mainly copper, zinc and tin, to human activities and the Iron Age was marked by the introduction of iron. Since then the use of metals has increased and culminated in the industrial revolution in the mid-eighteenth century which marked the onset of the industrial age in the western world. However, during the past 50 years, although metals were equally important to western economies as they had been previously, the amount of metals extracted annually in western countries has decreased significantly and metal mining activity shifted mainly to third world countries (in Africa, South America, Asia) and Australia, due to economic and environmental constraints. At the same time the role of industrial minerals has become increasingly important for the western economies and today, in developed EU countries, the production of industrial minerals has surpassed by far the production of metals. In some EU countries, metal mining activities have stopped completely. The importance of industrial minerals is expected to increase further in the future.
X-ray Powder Diffraction with Emphasis on Qualitative and Quantitative Analysis in Industrial Mineralogy
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Published:January 01, 2010
Abstract
Powder X-ray diffraction is the method of choice for characterizing the nature of crystalline solids and it can also be applied to non-crystalline solids. The method is ideal for analysing crystalline phases (e.g. minerals) because diffracted X-rays are direct probes of the repeating atomic units in solids. Qualitative analysis is based on the fact that each crystalline structure has a certain distribution of repeat distances which results in a diffraction pattern that is much like a fingerprint. The particular distribution and intensity of diffraction peaks is uniquely characteristic of each material. Quantitative analysis, i.e. determination of the amounts of more than one phase in a mixture, can be done because the diffraction intensities are directly related to crystal structure and the amounts of each phase. Quantitative analysis methods range from those using one or a few reflections to those using the entire diffraction pattern. The latter can employ either measured standard patterns or patterns calculated based on the crystal structures of the component phases, known as the Rietveld method. These full-pattern methods have important advantages as they use all intensity data in a pattern rather than one or a few of the most intense reflections. Some of the most troublesome systematic errors, including sample displacement, zero-point shift, and preferred orientation, can be refined, and the method yields unit-cell parameters of accuracy comparable to that obtained when using an internal d-spacing standard. The method finds wide application in industry, including modal analysis and compositional determinations of individual components using unit-cell parameter systematics. in addition, modern quantitative analysis methods can often be sensitive to amounts of <0.1 wt.%.
