Imitation Moldavite
Recently GIA’s Carlsbad laboratory received for identification a 46.13 ct yellowish green rough stone. The lack of a polished flat surface prevented a refractive index reading, while the specific gravity was measured as 2.45. Under microscopic examination, very few gas bubbles were found and some straight, approximately evenly spaced surface features were observed (figure 1).
Closer examination revealed these features were likely artificially acid-etched flow lines. The presence of gas bubbles coupled with flow lines led the author to infer an artificial glass or a natural glass, possibly moldavite, though moldavite has more natural-looking flow lines (figure 2). The SG reading was also slightly higher than the expected SG of 2.36 for moldavite. Additionally, moldavite typically contains numerous gas bubbles. Suspecting an artificial glass, the author analyzed the stone with a Fourier-transform infrared (FTIR) spectrometer. The FTIR reading showed absorption bands at approximately 2900 and 3480 nm, which confirmed an artificial glass.
Moldavites are a form of tektite, an impact glass created by the melting of rock caused when a meteorite strikes the earth’s surface. The most famous moldavites, found in southern Bohemia in the Czech Republic, were formed by the impact of the meteor that created the Ries crater 500 km away in southern Germany 14.7 million years ago. With rising prices for moldavite over the past few years, moldavite imitations have become more prevalent (Spring 2015 Gem News International, pp. 103–104).
