Diamonds are created deep inside the earth’s crust where they endure incredible conditions including high pressure (millions of atmospheres) and high temperatures (1000 – 1200 C.) The diamond’s crystal substance is composed of pure carbon in a packed tetrahedral symmetry. The natural process of diamond creation is incredibly slow, occurring over several million years and only a small percent of the diamonds formed are ejected to the earth’s surface by magmatic eruptions (figure 5). Due to the intense nature of these eruptions, a phenomenon called graphitization occurs. This means that the stone is harmed in some way, either at the surface, or inside the stone. Significant inclusions can affect the final diamond’s value.
An ideal diamond is one with perfect tetrahedral symmetry, resulting in a 100% transparent stone. However, perfect diamonds are almost impossible to come by. Some of the most valuable diamonds in the world have some sort of imperfection. Chemical contaminations are present in most diamonds. Usually it is graphite but it can also be nitrogen, and occasionally boron and additional elements. Some of these impurities, as well as imperfections in the diamond’s crystal structure, can result in the presence of a color in the stone.
Almost all diamonds contain nitrogen atoms, which replace a small percent of the carbon atoms in the crystal structure. This usually adds some yellow to brown color to diamond. Boron contamination on the other hand introduces a gray to blue color to the diamond. The plastic deformation of the diamond’s crystal will cause a brown color in the stone. This plastic deformation is found in about 1% of natural diamonds.
Though there are several causes for color within diamonds, most diamonds owe their colors to nitrogen atoms. For this reason, one of the main focuses of color enhancement treatments is on the very nature of the nitrogen atom in diamonds. The second most common cause for color is the plastic deformation of the crystal, which leads to a brown color.