If your sapphire has an aurora look to it, then it's more likely to be a sapphire blue crystal or rhinestone. Though I am not a gemologist, I do have an appraiser's license and work with jewelry. Faceted glass beads that have an added iridescent coating are called aurora borealis. The coating is used on beads and rhinestones and produces a multi color light reflection. The Aurora borealis means northern lights. The iridescent surface occurs when a very thin layer of metallic atoms are deposited on the lower surface of the stone. The process was invented by the Swarovski Co & Christian Dior in 1955. Most people relate Sapphire to the color Blue. Sapphire is a form of Corundum, readily available in an array of other colors: Pink, Golden, Green, peachy Orange, Purple and Colorless. These alternate colors are called 'Fancy Sapphire', or simply variations of the standard hues. Color change Sapphires are those which have two colors which are distinct when the light source is changed from fluorescent to incandescent. Generally, the more clear and vivid the color, the more valuable the fancy sapphire. If the color is in the pastel range, the clarity should be good: because in lighter tones any inclusions are more noticeable. If you had purchased this stone as an authentic sapphire and it has paperwork with it, and it was an immense amount for the stone; you should return it for a full refund. Hope some of this information has helped, good luck.

Not sure if you mean iridescence in light or variation in color. Iridescence as in it looks like oil on a puddle would mean its a crystal not a sapphire. Variation in color through the stone can actually be really valuable. I've seen stones that looked like a slice of watermelon, cool, pricey.