A colour-change sapphire and diamond ring

A colour-change sapphire and diamond ring The oval cabochon colour-change sapphire, <I>weighing approximately 17.20 carats</I>, in a collet mount between tapered baguette-cut diamond shoulders, <I>finger size N½</I> <I>Accompanied by report no. GRS2013-020649T from Gem Research swisslab (GRS), dated 2nd March 2013, stating that the sapphire colour changes from violetish-blue (daylight) to purple (incandescent) and no indication of thermal treatment was observed.</I>