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A new method in quantitative x-ray diffractometry has been developed which uses no "standard" minerals for calibration. Thus, this new method is diametrically different from the classical internal method of Klug and Alexander, which requires the similarity (in chemical composition, crystallinity, and degree of preferred orientation) of minerals used as "the standards" and in the unknowns. The method is based on the interrelationship between the weight percentages of constituent minerals in a rock and relative intensities of x-ray peaks arising from these minerals.
If the concentration in percent of mineral m in sample s is denoted as Xms, the mass absorption coefficient as µs, the intensity of a diffraction peak as Ims, and the instrumental (including structural and compositional characteristics of the constituent minerals) constant as Km, then the weight percentages of minerals in a rock can be obtained easily through a least-squares analysis, Xms = Ks/I^primems, where I^prime = Ims/µs. The µs can be measured readily from the Compton scattering intensity with an x-ray spectrometer.
Examples from a synthetic mixture, carbonate rock, and mudrock illustrate this new approach.
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