An additional source of color in diamonds is various deformations in the crystal structure of the diamonds. Diamonds with crystal structures that are not ideally tetrahedral can result in deformations and lead to the presence of color in diamonds. Plastic deformations, which are caused by the strain induced into the crystal from carbon atoms that deviated from the ideal position, can also create color in diamonds. These deformations can also create a dark brown color, figure 14, in the stone and reduce its quality and overall value. These deformations are not as stable as the ideal diamond should be. When thermally treated, these diamonds can transform from a deformed structure into a beautiful colorless diamond with the perfect tetrahedral crystal structure.
