The crystallization of natural diamonds have their own unique growth pattern that is similar to how tree rings are used to measure their age. Natural diamonds are born deep inside the earth and because they are under the influence of a variety of earth's environmental changes (temperature and pressure) until they come to the surface, there are no two diamonds that have the same growth pattern. However, if two diamonds are cut and polished from the same crystallization and placed with their table adjacent to each other in the correct position, you can see the growth patterns on the table going in the same direction. We use special observation equipment to confirm that they come from the same crystallization and this makes it possible for us to prove that two diamonds come from the same raw ore.
At CGL we call two diamonds that come from the same raw ore Twin Diamonds because they are just like twins.