Abstract
Infrared spectroscopy provides a means to distinguish natural from synthetic emeralds i n the range 2000-5000 cm -I , as determined b y a study of spectra obtained from 37 natural, 19 hydrothermal synthetic, and 38 flux synthetic emeralds from a variety of sources. The technique is nondestructive and, with Fourier transform instrumentation, extremely rapid in comparison t o most laboratory methods. It is especially useful for identifying stones that contain n o distinguishing inclusions. Various manufacturers continue to produce and introduce synthetic emeralds (figure 1 ). Although inclusions usually enable gemologists to distinguish natural from synthetic emeralds, flawless stones may be extremely difficult to identify by conventional gemological means. Laboratory methods (e.g., microprobe, X-ray fluorescence) that involve equipment that is generally too expensive for practical ownership by most gemologists can then be applied as a last resort. More than one of these has proved useful in separating synthetic from natural emeralds (Griffiths and Nassau, 1980; Kuhlmann, 1983; Schrader, 1983; Troup and Hutton, 1983; Stockton, 1984) , but the methods are generally time-consuming. By contrast, Fourier transform infrared (FTIR) spectrometry, especially when accompanied by an automated microbeam chamber, provides rapid, completely nondestructive results in less than five n ~i n u t e s (Fritsch and Stoclzton, 1987) .
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