Allochromatic gems are gems which have been coloured by impurities. If they had been entirely pure, they'd be colorless. The colour of all allochromatic gems is produced by defects. Thus, all shade in corundum is brought on by defects. Attractive piece of jewelry- nicely produced. Not much too flashy for https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share