X-ray Diffraction Study of Aquamarine from Shigar Deposits, Skardu Valley, Northwest Pakistan

Abstract

Samples of aquamarine collected from pegmatite rocks in Shigar mines, Skardu valley were investigated by
powder X-ray diffraction method. Qualitative phase analyses of the samples showed the presence of aquamarine as
major phase with quartz, talc and magnesite as minor phases. Lattice parameters were determined by employing CuKα
radiations in step-scan mode using a computer program ‘Powder’. The lattice parameters of the Shigar specimens (with
CuKα wavelength = 0.15418 nm) are a = 9.214 ± 0.002 (Å), c = 9.202 ± 0.002 (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.

Keywords: Shigar valley, aquamarine, beryl, powder diffraction, lattice parameters.