It has been estimated that only one in every 10,000 natural diamonds is classed as a fancy colour diamond. Over billions of years, all natural diamonds are formed through exposure to extreme forces of pressure and heat. Sometimes, on their long journey to the earth’s surface, such forces can cause uncommon distortions in the lattice of carbon atoms. Likewise, certain natural elements, such as nitrogen or boron, can saturate the diamond and alter its microscopic structure. These changes affect the way a diamond interacts with light, giving it its exceptional colour.
All natural fancy colour diamonds are rare, but some colours and depths of shade are rarer than others. Depending on hue, tone and saturation, they are awarded various grades, including fancy light and fancy through to fancy intense and fancy vivid. When a diamond has two or three visible colours in equal combination, you will see this reflected in its title, for example, a fancy yellow-green diamond. If it has a secondary hue, it might be characterized as a fancy brownish pink diamond or fancy intense orangey pink. Remember, however, that the last word in the laboratory’s colour description is the main colour. So pinkish brown is a brown diamond with a hint of pink, but a brownish pink diamond is a pink diamond with a hint of brown.