This research of yellow sapphires was determined by the lack of clarity from the literature as to the origin from the yellow coloration. In retrospect, this uncertainty was the result of 3 components. To start with, the Fe3+ concentration in natural stones spans A selection of around four–4750 ppma, but https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share