Allochromatic gems are gems which have been coloured by impurities. Should they have been completely pure, they'd be colorless. The colour of all allochromatic gems is produced by defects. Consequently, all shade in corundum is because of defects. Therapy: Nearly all gemstones are handled usually dealt with to reinforce their https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share