Allochromatic gems are gems which have been coloured by impurities. When they have been fully pure, they would be colorless. The color of all allochromatic gems is made by defects. Consequently, all colour in corundum is because of defects. Want another excuse to purchase our sunny types? Yellow sapphires can https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share