This research of yellow sapphires was inspired by the lack of clarity from the literature as on the origin on the yellow coloration. In retrospect, this uncertainty was the results of 3 aspects. To start with, the Fe3+ concentration in natural stones spans a range of approximately 4–4750 ppma, but https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share