gems, corundum, sapphire, origin determination, Burma.12, India.12, Kashmir.12, Madagascar.12, Thailand.12, Sri Lanka.12, Nigeria.12, Australia.12, Ethiopia.12, analytical, provenance

Geographic origin determination, one of the most pressing issues facing modern gemological laboratories, is especially challenging for blue sapphire. Reliable origin determination requires careful analysis of a stone’s inclusions and trace element chemistry as well as spectroscopic data. Some stones have characteristic inclusion scenes or trace element chemistry that make it easy to determine their origin, but in many cases there is significant overlap for blue sapphire from distinct geographic localities. The most commonly encountered inclusions are rutile silk and particle clouds. In some stones the silk or clouds may take on a distinct appearance and the origin may be accurately determined. But in many cases the evidence presented by inclusions within a stone is ambiguous. This contribution outlines the methods and criteria used at GIA for geographic origin determination of blue sapphire.