Allochromatic gems are gems which have been colored by impurities. Should they had been entirely pure, they'd be colorless. The color of all allochromatic gems is made by defects. Therefore, all shade in corundum is because of defects. Burma has been renowned for producing a variety of precious gemstones, from https://one-bookmark.com/story18022348/top-sri-lankan-pukhraj-secrets