Allochromatic gems are gems which have been coloured by impurities. If they were completely pure, they might be colorless. The color of all allochromatic gems is made by defects. So, all colour in corundum is a result of defects. Pukhraj stones are considered to become potent talismans that carry fantastic https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share