Diamond Colours: What are the Different Colours of Diamonds?
Naturally coloured diamonds are precious stones that have a tint or hue caused by natural processes in its development. Formed when foreign particles are present during the crystallisation process, the white gem takes on a coloured hue. Heat and pressure is also able to alter the colouring of a diamond. This article takes a look at the different shades along the diamond colour scale, and the processes unique to their creation.
Green diamonds are formed due the stone being exposed to natural radiation within the soil located just before the earth's crust, known as the continental crust. This natural radiation is what causes the diamond to reflect red and yellow light, and therefore give the diamond a green hue.
Violet and Purple Diamonds
Purple diamonds are created as a result of lattice distortion within the stone. New studies are revealing that the presence of hydrogen during the crystallisation process may also result in diamonds gaining a purple or violet tint.
Orange and Yellow Diamonds
Diamonds that are naturally yellow or orange in colour are created when nitrogen is present during the crystallisation process. Nitrogen atoms arrange in such a way during the diamond’s formation that blue light is absorbed, and gives the diamond a yellow tint. The resulting, often brilliantly coloured, yellow stones are also known as Canary Diamonds. Orange diamonds are created in a similar way using a specific nitrogen formation which absorbs both the blue and yellow light to produce an orange stone.
Grey and Blue Diamonds
Boron is the active element which creates blue coloured diamonds. The boron bonds to the carbon within the crystalline structure to absorb red, green and yellow in the colour spectrum and produces a blue diamond.
Brown, Red and Pink Diamonds
These diamonds get their natural colour from the intense pressure and heat which is applied during the formation process. The heat and pressure causes distortion within the crystal lattice, which is what absorbs green light and therefore gives the stone a pink, red or brown hue.
Beyond the above shades, natural coloured diamonds are available in an unlimited amount of hues and intensities. The crystallisation process, trace minerals present in the soil, heat, and natural radiation levels in the earth's mantle are some of the many factors that make up a stone’s colouring. Because scientists are unable to observe natural diamonds being formed, the exact properties that are required to create a specific coloured diamond are almost impossible to determine.
Natural coloured diamonds are available in 11 base colours forming the diamond colour chart; yellow, green, brown, orange, purple, pink, blue, red, violet, white and black. Diamonds are also further graded by the intensity of their colour. There are nine standard intensity levels:
As such, a fancy intense pink diamond will appear very different from a faint pink diamond. White diamonds are also graded in 17 ways, as each stone is given a grade from D-Z based on how close to “colourless” the stone is. A single diamond can also have dominant colours, secondary colours and third colours. Taking all of this into consideration, there are over 7000 different types of diamond colours available (by grading standards). Diamond cuts will also affect the appearance of the colour of a diamond, changing the way it reflects light and its own natural hue.
Diamonds can also be colour treated and enhanced in order to alter their colour. The main method used to colour precious stones is called high-pressure high-temperature processing (HPHT). The same process can also be used to remove the colouring from natural stones and is commonly performed with light brown diamonds, which are typically cheaper than white diamonds, with HPHT processes removing the natural colouring to create a more sought after white diamond. Diamonds which are naturally coloured are often more valuable than synthetically coloured stones, both for their authenticity and natural rarity.