PIXE studies of emeralds

A total of 56 natural emeralds and 26 synthetic emeralds were studied by PI XE. From the PIXE spectra and the concentrations of 33 elements, i.e. Sc, T i, V, Cr, Mn, Fe, Ni, K, Rb, Cs, Ca, Sr, Ba, Co, Cu, Zn, Y, Zr, La, Ce, Ga, P, S, Cl, As, Br, Mo, W, Pb, Bi, Pt, Au and Rh, obtained from the hulk ana lyses of inclusion-free regions of the stones, criteria for differentiating between natural and synthetic emeralds and among different localities of n atural emeralds were deduced. The use of concentrations of only three chrom ophoric elements, Cr, Fe and V, allowed us to attribute Pakistan emeralds, Chatham, Gilson, Taiwan and Lennix flux emeralds and a mixed group incorpor ating Russian flux and Russian hydrothermal emeralds. We then investigated all 32 elements (Rh was not detected in all the samples) through principal component analysis (PCA), which allowed us to specify whether an emerald wa s natural or synthetic in the first place and we were then successful in at tributing the stone, as a second step, to four localities for natural stone s, and to eight types for synthetic stones, one of which was a mixed group. The PCA of a reduced set of six elements, Cr, Fe, V, Mn, Ti and Cl, allowe d us to attribute Pakistan emeralds, Taiwan flux emeralds, Biron hydrotherm al emeralds and Biron hydrothermal emeralds measured at the boundary, and L echleitner emeralds. This PCA together with the study of the correlation of the three chromophoric elements, Cr, Fe and V, allowed us to attribute Col ombian and Pakistan emeralds and all synthetic emeralds, which was useful a nd convenient in real-life testing of unknown emeralds. Copyright (C) 2000 John Wiley & Sons, Ltd.