X-ray diffraction study of emerald from Mingora and Charbagh deposits, Swat valley, Northwest Pakistan
Keywords:
Swat Valley; Mingora; Emerald; Powder diffraction; Lattice parametersAbstract
Samples of emerald collected from carbonate-talc rocks in Mingora and Charbagh mines in Swat valley were investigated by powder X-ray diffraction method. Qualitative phase analyses of the samples showed the presence of emerald as major phase with quartz, talc and magnesite as minor phases in Mingora, and emerald as major phase with traces of quartz and talc in Charbagh sample. Lattice parameters were determined by employing CuKα radiations using a computer program 'Powder'. The lattice parameters of the Mingora and Charbagh specimens (with CuKα wavelength = 0.15418 nm) are: a = 9.258 ± 0.009 (Å), c = 9.191 ± 0.017 (Å) and a = 9.259 ± 0.005 (Å), c = 9.214 ± 0.006 (Å) compared to NBS (National Bureau of Standards) beryl data a= 9.215 Å, c =9.192Å. The deviations in the unit cell dimensions (especially the increase in a) of the samples are attributed to the presence of additional components (Cr, Fe, Na and Mg) detected by X-ray fluorescence method.
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