Colored Diamonds

by Neelanjana Ghosh

Only 1 percent of the world’s total diamond is colored, which makes these gems a rarity and their value priceless. Among all the colors of diamond found on earth red is probably the rarest and therefore most sought after. There is a collection of only thirty-five exquisite pieces of red diamonds across the world. Found by a farmer from Brazil, the Moussaieff Red diamond weighs 5.11 carats and is the largest red rock in the world.

Colored diamonds are one of the most coveted treasures one can possess and they are amongst the world’s rarest gemstones. Extremely rare and deemed equally precious by investors, collectors and connoisseurs alike are the world’s most nebulous and sought after gemstones. A colored diamond is an investment and an heirloom for a lifetime- or several lifetimes in case of the latter. It is a known fact that amongst 10,000 carats of diamonds mined only 1 carat is colored marking once again this gem’s extreme rarity. Colored diamonds are also termed as fancy diamonds; and these diamonds range in vibrant hues of red, blue, green, purple, yellow and many other shades as well.

Colored diamonds are graded on a scale of fancy, vivid and intense- based on their hue and saturation of color. They owe their color to the presence of trace elements within the diamond’s carbon crystal structure. Yellow- the most common color found is due to the presence of Nitrogen as an impurity within the crystal lattice of the diamond. Blue and grey colors are due to the presence of Boron or (rarely) Hydrogen. The color green is caused due to a phenomenon called ‘ vacancy color centre’ in gemological terms. What happens in this case is a vacancy within the atomic structure of carbon. Pink, mauve and brown colors in diamonds are caused by plastic deformation, ie; a distortion of the internal structure of the diamond.

Diamonds are formed about 170 to 200 kms below the surface of the earth and reaches the earth’s surface through volcanic eruptions in kimberlite stones. The volcanic eruptions which carried the diamonds to the surface of the earth is speculated to have occurred almost a million years ago and so most of the natural diamonds are quite logically a billion years old. The diamond ore is crushed with a lot of care to preserve and protect the diamond within. Only 1 percent of the world’s total diamond is colored, which makes these gems a rarity and their value priceless.

Among all the colors of diamond found on earth red is probably the rarest and therefore most sought after. There is a collection of only thirty-five exquisite pieces of red diamonds across the world. Found by a farmer from Brazil, the Moussaieff Red diamond weighs 5.11 carats and is the largest red rock in the world.

Pink diamonds are also highly sought-after and treasured again due to rarity and appealing color. The Argyle mine in Western Australia owned by Rio Tinto is the leading producer of the world’s pink diamonds and some blues too. They hold tenders to auction off these rare gems as and when the stocks are accumulated. The largest pink diamond in the world weighs around 59.60 carats and took twenty months to extract it from the ore in order to protect and preserve it

Due to the rarity and high market value of the stones, diamonds are treated to create color. One such treatment is the HPHT treatment- or the High Pressure High Temperature treatment. What happens here is the diamond is subjected to high pressure and high temperature to alter the its crystal structure and make brownish diamonds colorless and diamonds with nitrogen into an intense yellow-green color.

Another method to induce or improve color is by irradiation by atomic particles. This method produces color by altering or damaging the crystal structure of the diamond. The color can be further modified by subsequent heating. Irradiation and heating can only be used to change or intensify color in diamonds, it cannot be used to lighten an existing color.

Treatments are a part of the diamond trade and acceptable as long as the seller ‘discloses’ this to the buyer, or the fact is clearly mentioned on the identification report. Most reputed gemological laboratories will disclose treatment on the certificate for a fancy colored diamond. also these diamonds being expensive and big-ticket items are rarely sold without a certificate.

Of course an untreated diamond will cost significantly more than a treated stone. However color treatments are permanent and to some extent irreversible, so its alright to invent in one of these stones as long as one is aware of the treatment carried out on it.