Geographic Origin Determination of Blue Sapphire

GEMS & GEMOLOGY WINTER 2019 The twentieth century witnessed a surge of discoveries of blue sapphire deposits around the world. As the gem trade has evolved alongside these developments, geographic origin determination has become a major consideration in buying and selling sapphires. In some cases, the value of a stone can depend strongly on its origin, such as the Kashmir sapphires shown in figure 1. The trade largely relies on reputable gemological laboratories to make these origin determinations, which are based on comparison with extensive reference collections (see Vertriest et al., 2019, pp. 490–511 of this issue) and advanced analytical methods (see Groat et al., 2019, pp. 512–535 of this issue). After more than a decade of efforts by GIA’s field gemology and research departments to acquire reliable samples in the field and collect reference data, blue sapphire remains one of the greatest challenges when it comes to origin determination. The following sections will detail the origin data GIA has collected for blue sapphire and describe the laboratory’s methodology for using this data in geographic origin determination.