Do you know why diamonds are used for cutting glasses? Well, the diamond is the simplest and most distinctive of all gemstones. It is strong, brilliant and dazzling. Diamonds are held together so tightly that they are incapable of absorbing visible light and are therefore colourless. Also, an infinite array of carbon atoms linked in a rigid framework extending in all directions makes the diamond the hardest substance known. That is why diamonds are used for cutting glasses.