Pure diamonds are colourless. Colourless implies that they do not absorb light waves, but rather reflect them towards the observer who consequently sees a white light, or what the human eye interprets as colourless.
Unlike pure diamonds, blue diamonds absorb all light wavelengths except blue. Impurities, present in the molecular structure of diamond are the source of their light absorption. In the case of blue diamond, the impurity is boron.
Red and pink diamonds
The presence of hydrogen in a diamond produces purple hues. However, the extreme pressure to which diamonds are subject during their creation can abnormally compress the structure creating red our pink stones.
The red diamond is the rarest of all coloured diamonds. To date, only 20 stones have been certified as red diamonds.
Red diamonds are priceless. In 1987, a 0.95 carat red diamond was auctioned for a million dollars. In 1996, Christie’s sold a 0.25 ct, oval cut red diamond for $326,800.
The most famous red diamond is Moussaieff Red Diamond.
Pink diamond deposits are also very rare.
Celebrities like Jennifer Lopez, who in 2002 was offered a 6.1 ct, pink diamond mounted on an engagement ring, have contributed to the fame of these diamonds throughout the world.
The most important deposits of pink diamonds can be found in Brazil, Australia, Russia and Africa (Tanzania).
Diamonds formed over millions of years may undergo natural radiation that changes the colour to green.
Green diamonds are among the rarest natural diamonds and depending on the intensity and purity of the colour, prices can be extortionate.
The green colour is caused by natural exposure to radiation from uranium.
The presence of nitrogen can give a yellow colour to the diamond.
Yellow diamonds classified according to four levels of colour: Fancy Light Yellow, Fancy Yellow, Fancy Intense Yellow and Fancy Vivid Yellow. Although the yellow colour is not desired in a white diamond, canary yellow diamonds have long been recognised and appreciated by collectors; the more intense the yellow colour, the higher the price.