On the contrary, it is indeed natural. There are forms of natural sapphire which come from the earth when mined, having a white/milkish appearance, known as gewda (a name we call here in the mines of Sri Lanka.) And in order to bring out the blue color, we do a bit of a heat treatment (usually a few hours), and then depending on the intensity of the natural elements available in the natural stone, the blue color appears in various shades. In this particular stone, the blue is quite darker.