Coloured Diamonds
Natural Color Diamonds span the spectrum of the rainbow, though just about one out of every 10,000 naturally produced diamonds possesses enough color to be classified as a ‘fancy colored diamond’.
Color is a continuum that can be described and defined through three attributes; hue, tone, and saturation.
Hue refers to the dominant color of a stone that permits them to be classed as pink, yellow, blue, green, red, or anything in between.
Tone represents how light or dark a stone appears, which depends on how much black, grey, brown, or white is present.
Saturation describes the strength or intensity of the hue or main color. The saturation of lightly toned diamonds can vary from light to intense and vivid. Darker diamonds will range from deep to dark.
Red diamonds are considered one of the rarest diamonds in the world. They are found mostly from the Argyle Mine in Western Australia, and occasionally from the Minas Gerais in Brazil. Red diamonds exhibit many of the same characteristics as pinks, however they have a lower tone and higher saturation.
Every fancy color diamond, apart from red, has the prefix "intense" or "vivid" in its color grading scale. Red diamonds, though, are never noted as being intense or vivid because gemmological laboratories consider the red color itself as intense or vivid. The largest known red diamond is the Moussieff Red, a triangular 5 carat stone, while the vast majority of red diamonds are less than ½ carat in size.
For every million carats of rough diamond mines in the world in a year, only one carat of pink diamond is recovered. The unique quality of the pink stone is derived from a distortion in the molecular structure of the diamond following formation in the earth’s mantle or during their ascent to the earth’s surface. This process is referred to as plastic deformation much like a moulding a clay. The degree of the distortion in the structure impacts the way that the stone reflects light and the resulting color.
Pink diamonds have been found all over the world. The Agra, found in India, is one of the first documented pink diamonds. This 28 carat-gem is renowned for its combination of strong color and amazing size. Pink diamonds have also been found in Brazil and southern Africa, but it was not until the opening of the Argyle mine in Australia in 1985 that there was a consistent source. Argyle is expected to close in the coming years, preserving the rarity of the pink diamond.
The vibrancy and energy of Orange Diamonds is incomparable. Only a lucky few have ever seen a pure orange diamond because the stones are rare and elusive. Most orange diamonds come with a modifying color, such as, yellow, brown, and sometimes pink.
The vast majority contain some nitrogen, and they group themselves in an unambiguous way with the carbon atoms during the formation of the diamond, continuing until after the diamond is formed. These nitrogen arrangements absorb light in the blue and yellow region of the spectrum producing an orange color.
Orange diamonds are somewhat of an anomaly. Although the orange hue is not as rare in nature as some other hues, the GIA rarely grades an orange diamond as “pure” orange. This makes any pure orange diamonds even rarer than the elusive red diamonds.
Most Orange Diamonds come from Africa. The interest in this color surged in 1997 with the auction of the Pumpkin Diamond, which was eventually worn by the best actress of Oscars, Halle Berry, in 2002.
Yellows are the most popular of all natural colored diamonds; and also by far the most commonly produced of fancy color diamonds. It is estimated that around 60% of all natural colored diamonds belong to the fancy yellow category.
A diamond's yellow color is the result of nitrogen molecules absorbing blue light, making the diamond appear yellow (yellow being the complement of the color blue). Yellow diamonds can contain orange, green, or brown modifiers.
The most notably large and intense yellow diamonds have been discovered primarily in South Africa. The Allnatt, a 101 carat cushion shape fancy vivid yellow diamond is perhaps the most significant yellow diamond in history, named after its original owner Major Allnatt in the 1950s.
Natural green diamonds are extremely rare and desirable. The beauty of these gems has spawned unprecedented desire and unparalleled prices among collectors and connoisseurs.
Green diamonds acquire their color after their trip to the surface of the earth where they rest in the ground near naturally occurring radiation. This radiation pushes into the diamond causing absorption in the red and yellow spectrum to produce its trademark color. Green diamonds are often graded with color modifiers such as bluish green, yellow-green, or brown and grey traces too.
The Dresden Green is the most famous green diamond, weighing about 41 carats. It is often referred to as the cousin of the Hope Diamond for its historical importance.
Blue diamonds have a long and fascinating history, but have only recently been available on a wide scale in the market on a consistent basis. Demand for blue diamonds has greatly increased in the past 10-15 years, thanks in part to celebrity attention, record breaking auctions, and price speculations.
The vast majority of blue diamonds’ owe their color to the presence of boron. The bonding of boron to carbon causes absorption in the red, yellow, and green parts of the spectrum producing a blue color. Blue diamonds may contain a grey, violet, or greenish complementary color. Blue diamonds are almost always type II b, and do not contain any fluorescence and generally have few inclusions.
The Cullinan mine and Golconda region are the most notable areas where blue diamonds have come from. The most famous blue diamond in history is the 45 carat "Hope Diamond". The Argyle mine in Australia extracts metallic blue diamonds.
Chameleon diamonds are considered collector’s items, consisting of combination of grey, yellow, orange and green. They can change color from orange or yellow to olive and vice-versa, depending on the lighting or temperature. The value is only known by how saturated the stone is in its normal state, and while changing the temperature.
It is believed that the color-changing effect is due to a higher than normal amount of hydrogen impurities. Chameleon diamonds are sourced from the Democratic Republic of Congo, Central Africa and Brazil.
