What Makes a Diamond Blue?

These days, fancy colored diamonds are the hottest rage. In fact, almost every record-breaking diamond price reached at auction in the past ten years has gone to a fancy colored diamond. Colorless diamonds – long thought of as the most pure, and therefore, the most coveted – are now the pasty monarchy of yesteryear. But what exactly gives a diamond its color, or lack thereof?

The first thing to know is that aside from the purely synthetic, there are two kinds of colored diamonds, those which are naturally occurring, and those which are irradiated using diamond enhancement techniques. While getting work done on a diamond may not be as obvious as it is on a Hollywood celebrity, the appeal of synthetically colored diamonds for serious buyers is practically nil. Those who want to invest in fancy colored diamonds are looking exclusively for stones with GIA or AGL certificates, which include the diamond’s origin and the diamond’s color origin. The color origins of naturally occurring diamonds depend on the colors themselves. The following is a list of material properties that determine the color of a diamond.


Diamonds in the normal color range

In a way, colorless diamonds really are the most pure because their crystal lattice structure is completely intact and unadulterated by impurities and defects. A diamond’s crystal lattice is extraordinarily strong, however, during the diamond’s growth phase, it is possible for impurities such as nitrogen, boron, and/or hydrogen atoms to be introduced, forming a carbon flaw in the crystal lattice. Nitrogen, the most common impurity, is responsible for the yellow and brown color in diamonds. If the Nitrogen concentration is relatively low, the diamond may still fall under the D-Z color range. However, if it is relatively high, the discoloration will be much more vivid and the diamond will be classified as a fancy colored diamond. Fancy colored diamonds are graded on a completely different color scale, one that favors the intensity of color, rather than its absence.

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 Pink, Red, and Brown Diamonds

Fancy colored pink, red and brown diamonds get their color from plastic deformation, a process of sustained force on the crystal structure that is believed to occur within the Earth’s mantle. Pink diamonds are commonly found in Australia and Venezuela but are extremely rare, accounting for about 1.8% of gem diamonds. It’s no wonder the 24.78-carat, fancy intense pink diamond – known as the Graff Pink – is the most expensive single jewel ever sold at auction, that is after Laurence Graff acquired it for a whopping $46 million.


Black Diamonds

Carbonado, or black diamonds are not actually black in color. In fact, they get their dark color from numerous inclusions within the stone. These inclusions are usually composed of foreign minerals such as olivine, garnet and ruby, which can potentially compromise the structural integrity of the stone. It is for this reason that black diamonds have never garnered much attention or value.

Blue Diamonds

Even more rare than fancy pink diamonds – but also found in Australia – are fancy blue diamonds, accounting for about 0.1% of all gem diamonds. These stones get their steely blue to grey color from an abundance of boron atoms found within the crystal lattice. According to GIA, the Hope Diamond, widely considered the most famous diamond in the world, is fancy dark grayish blue in color. The 45.52-carat diamond is estimated to be worth $250 million and was formed within the Earth approximately 1.1 billion years ago.


Purple Diamonds

There are two kinds of natural fancy purple diamonds: purple and violet. These stones are scarcely found in Australia and are usually no more than a carat or two in weight. Fancy purple diamonds tend to have reddish or pinkish hues, which is a product of the same plastic deformation in their crystal lattice that is observed in red, pink and brown diamonds. The color observed in fancy violet diamonds is owed to the presence of hydrogen atoms within the lattice, giving the stone a violet hue that leans toward the blue-grey spectrum.


 Green Diamonds

Last and definitely least prevalent are fancy green diamonds, which are almost always green due to artificial diamond enhancement techniques. However, in some rare cases irradiation can occur naturally due to radiation burns caused by proximity with uranium ore. As seen in the Dresden Green Diamond, a 41-carat natural green diamond, discovered in India in the early 18th century.


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