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
You need to get a “color-stability” test for the stone. Only sapphire orangish color of which is chemically stable can be labeled as a “padparadscha” sapphire by many prominent gem labs like GRS, Lotus, GIA et cetera.
Is there such test!! Which labs does it ? Or is it simply a treatment disclosure?
Padparadscha-Like Fancy Sapphires with Unstable Colors: https://gem-a.com/images/JoG/JoG2018_36_4.pdf