One of the most notable is that it is singly refractive. This means that light is not split when it enters the stone. Most diamond simulants such as C.Z. and Moissonite are doubly refractive. If you look through zircon or synthetic rutile under magnification, in most directions you will see double images of the facets on the other side. The strength of the doubling depends on the material.
Most people think of diamonds as a beautiful colorless gem.
Diamonds can have some very interesting optical properties especially under fluorescent lighting, glowing green or blue and rarely orange or pink. Diamonds are occasionally enhanced to improve color and clarity. The diamond is extremely hard with a rating of 10 mohs and is considered to have good toughness in cleavage directions and exceptional toughness in all other directions. Click to enlarge Click to enlarge Click to enlarge Click to enlarge May Emerald Click to enlarge In ancient Egypt this stone represented fertility and rebirth. This stone was also used to treat eye ailments.