Please note: The causes of colour here are just a few of the many causes of colour in natural coloured diamonds. There are other natural defects that can produce colour. It’s possible to also change or induce color in diamonds by treatments that include irradiation, heating, and coating – and by combinations of multiple treatments. There are many causes of colour in diamonds, and researchers are only beginning to understand them.
The Colour Diamonds made available through Coral Bay are all Natural & Untreated Colour Diamonds.
Yellow is the second most common natural colour in diamonds. The colour is usually caused by nitrogen atoms substituting for carbon in the diamond crystal lattice. This defect causes diamond to selectively absorb blue light and selectively transmit yellow.
Pink is a very rare natural colour in diamonds. It occurs when the diamond is subjected to stress within the Earth, and those forces cause glide planes of carbon atom displacement within the diamond crystal. When light passes through the planes, red light is selectively transmitted. The red light appears pink when the selective transmission is weak. The selective transmission is rarely strong enough to produce a red colour.
Blue diamonds are rare in nature. The blue colour is most often caused by boron atoms substituting for carbon atoms in the crystal lattice of diamonds that have formed at extreme depths. As little as one boron atom per million carbon atoms can produce a noticeable blue colour. Boron in the diamond crystal causes the selective absorption of red light and the selective transmission of blue.
Green diamonds are very rare in nature. The colour usually develops when high-energy radiation emitted by nearby radioactive mineral grains penetrates the diamond. The radiation knocks carbon atoms out of their position in the diamond crystal lattice, and that defect causes the diamond crystal to selectively absorb red light and selectively transmit green. Green colour can also be a result of defects produced by the presence of nitrogen, hydrogen, or nickel within the diamond crystal.
Orange diamonds are very rare. The defect(s) that produce the orange colour have not been determined with certainty and may vary from one orange diamond to another. The defects in orange diamonds cause them to selectively absorb blue light and selectively transmit orange.
Brown is the most common natural colour in diamonds. The colour develops when plastic deformation creates planes of missing and displaced carbon atoms in the diamond crystal lattice. These are known as glide planes, and they are where the brown colour is concentrated. They can appear as a series of parallel colour bands in the diamond known as “graining”.
Violet is one of the rarest natural colours in diamond. It is sometimes caused by substitution of hydrogen in place of carbon in the diamond crystal lattice.
Gray diamonds (sometimes also spelt grey), like all colour diamonds, get their colour from the inclusion of foreign elements during the diamond’s formation under the Earth. In this case, the gray colour is caused by the inclusion of hydrogen, although it may also be caused by boron
Purple is another rare colour in diamond. In a study of 50 purple diamonds by GIA, they often found H3 and N3 colour centers, sufficient enough to influence colour. Purple diamonds and some pink diamonds modified by purple often exhibit colour concentration along glide planes of carbon atom displacement.
Red diamonds are extremely rare in nature, and they are the most valuable diamonds when in a pure hue. Like pink diamonds, they have been subjected to stress which deformed the diamond crystal lattice, causing glide planes of carbon atom displacement. When light passes through the planes of displacement, the red wavelengths of light are selectively transmitted. Weak transmission of red light will produce a pink diamond.
Black diamonds with a natural colour usually contain such a high density of mineral inclusions that very little light passes through the gem. Common inclusions in black diamonds include graphite, pyrite, or hematite. Black colour in heavily fractured diamonds can be caused by graphitization of the fracture surfaces.
White diamonds occur in nature when the diamond has dense clouds of fine, reflective inclusions. The numerous inclusions can interfere with the passage of light and give the diamond a translucent or opalescent appearance
