Allochromatic gems are gems which are colored by impurities. Should they were entirely pure, they might be colorless. The color of all allochromatic gems is made by defects. As a result, all shade in corundum is due to defects. Beware glass-stuffed Ceylon Yellow Sapphires. They might glimpse shiny Nonetheless they https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share