Nuclear microscopic studies of inclusions in natural and synthetic emeralds

Abstract

Maps recorded by micro-proton-induced x-ray emission (micro-PIXE) were obtained for different chemical elements for natural and synthetic emeralds. Eighty pieces of natural and synthetic stones were examined. The following inclusions and minerals were observed: (1) color zoning/elemental zoning; (2) brine components; (3) calcite/dolomite; (4) chromite/magnetite; (5) pyrite and the accompanying sphalerite/wurtzite; (6) mica (biotite, phlogopite and muscovite); (7) feldspar (orthoclase and anorthite of plagioclase); (8) flux residues/nutrient residues; and (9) seed crystal. These (a) demonstrated the power of micro-PIXE in revealing inclusions in emeralds, which was useful for easy and unambiguous identification, and which made the identification of inclusions in rough stones possible; (b) provided some criteria for discrimination between natural and synthetic emeralds; and (c) gave the source of some chemical elements, so that their presence derived from the PIXE spectra would be further supported (e.g. Cl in the brine component in natural and flux grown emeralds; Cl was previously said to be present only in hydrothermal grown emeralds). Furthermore, the present work showed the power of micro-PIXE in the in situ study of minerals. Copyright © 2000 John Wiley & Sons, Ltd.