Allochromatic gems are gems that are colored by impurities. If they had been completely pure, they would be colorless. The colour of all allochromatic gems is produced by defects. Thus, all coloration in corundum is due to defects. Require one more reason to order our sunny styles? Yellow sapphires are https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share