You will need to find out whether this is synthetic or natural, so bone up on your gemology or send the stone out for an ID. Since this is a 4+ ct sapphire, if you can determine that it is natural, you should send it out to GIA or another premium lab for ID, since they can specify heat or no heat, diffusion treatment or not, and render a decision on the color. You will need their report for insurance purposes or in order to sell the stone. -royjohn