A Review of Analytical Methods Used in Geographic Origin Determination of Gemstones

GEMS & GEMOLOGY WINTER 2019 In gemology, “origin” refers to the geographic locality of a gemstone deposit (Hänni, 1994). Origin determination of colored gemstones began with Gübelin and SSEF (both in Switzerland) in the 1950s and with AGL (New York) in 1977 (Schwarz, 2015). Origin determination is of increasing importance in today’s market, and for many gems this information is considered either a value-adding factor or a positive for the salability of a gemstone (Hainschwang and Notari, 2015). Origin determination is often possible because there is a close relationship between the environment of crystallization, especially the mineralogical and chemical composition of the host rock, and the properties of the gemstones that can be studied in the lab, often using sophisticated equipment (Hänni, 1994). In this paper we review the analytical techniques (figure 1) commonly used to characterize gem materials, with a specific focus on geographic origin determination. We also review the physical and chemical properties of corundum and emerald, which have the greatest demand for origin determination. Finally, we provide examples of origin determination of corundum and emerald from the literature to illustrate how these analytical methods are applied to the problem of establishing origin.