Allochromatic gems are gems which might be colored by impurities. If they were being totally pure, they might be colorless. The colour of all allochromatic gems is made by defects. Hence, all coloration in corundum is because of defects. As indicated before, Along with the absorption cross section boost with https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share