Diamonds that are naturally colored undergo a very interesting process. As you probably know, the creation of a single diamond is a concentrated and particular process. The formation of diamond crystals from carbon matter is thought to take millions of years, and scientists now know that these precious stones are actually formed in the upper mantle of the Earth, so far below the surface that we actually can’t reach them. So they may grow in fits and spurts over the course of hundreds of millions of years or they may only take weeks to form under the intense heat and pressure. In any case, they find their way into the upper layers of the Earth’s crust through a process of underground volcanic eruptions, the likes of which have not been seen, well, ever (at least not by man). This is why diamonds are a rare and finite commodity.
But what makes them colorful (or colorless)? While the main component necessary for diamonds to form is carbon, there are often other elements at play that can radically affect the composition of a crystal. A natural stone that only contains carbon will be perfectly colorless. But when nitrogen is added to the mix, for example, you’ll end up with a yellow diamond. And the presence of boron will produce bluish tones. Almost any color can be created under the right set of elemental circumstances. However, there are a number of other factors that also come into play.
Inclusions can dramatically enhance color. While they are considered undesirable in colorless stones (and noted as flaws), they can actually add depth and intensity to a diamond that already has some color. The most brilliant tones are produced as a side effect of an inclusion. Then there are environmental factors that come into play. For example, more intense heat and pressure can exacerbate the process, which is why colored stones can range from pale to extremely saturated tints. Radiation in the immediate environment can cause a diamond to take on a greenish hue, and in the case of pink diamonds, the coloration is thought to be the result of intense stresses on the stone during formation that cause electrons to refract light at the red end of the spectrum.
Because the circumstances required to alter colorless diamonds is so precise, it’s no wonder that these stones are so precious and valuable. They make up only a small percentage of diamonds that reach the retail market every year, and like anything rare, they can be quite expensive. For this reason, most people still prefer the tried and true colorless or nearly colorless stones that are recognized around the globe as diamonds.