This analyze of yellow sapphires was enthusiastic by the lack of clarity within the literature as to the origin on the yellow coloration. On reflection, this uncertainty was the result of a few aspects. To start with, the Fe3+ focus in natural stones spans a range of approximately four–4750 ppma, https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share