Fancy Diamond Colour
Colour in diamonds is primarily caused in three different ways. It may either be due to physical stress distorting the crystal or inflicted by natural radiation damage. Alternatively, trace elements may enter the structure. The only three small and mobile enough atoms able to penetrate the tight, closely-knit diamond lattice are nitrogen, boron and hydrogen.
Fancy Colour diamonds, unlike ‘ordinary’ D-Z diamonds, are judged for the presence of colour. They are always assessed face-up for their apparent colour and are classified according to the Gemological Institue of America either as faint, very light, fancy light, fancy, fancy intense, fancy vivid, fancy deep or fancy dark. These prefixes are a combination of saturation which denotes the actual intensity (or purity) of a particular hue and tone which describes the relative lightness or darkness of a colour ranging from faint which is just a little more than white to dark which essentially is just a little less than being black. Together saturation and tone define the level of brightness of a colour.
To complete a description of the visual sensation of colour as accurately as possible both small and capitalized colour descriptors are used as necessary. They describe the dominant and secondary (modifying) hues present within a diamond. Dominant hues are always capitalized and hyphenated whenever the actual colour present is a near-equal combination of two distinct hues. A good example would be the colour ‘Aquamarine’ which would be described as ‘Green-Blue’ on a grading report. The last mentioned colour is always the slightly overwhelming hue. A complete colour term may, if necessary, also include up to two secondary hues such as ‘greyish greenish’, with the first one being the weaker of the two. Combining all these aforementioned technical descriptors we would arrive at a diamond’s complete colour description for example ‘fancy greyish Green-Blue’ which for communication purposes would give anyone a good idea which colour to expect. Additionally, the colour of the diamond may be further described as even or uneven. Colour zonation can be an issue in coloured diamonds and an even colour distribution is strongly favoured.
Primary hues like red, blue, yellow are always more vivid than secondary hues. The point where both tone and saturation of a given hue reach their combined maximum is scientifically termed the ‘gamut limit’. This maximum of ‘colour radiance’ as it may be aptly called differs for the varying spectral hues. Stones that reach this maximum brightness are usually known as being ‘vivid’. ‘Intense’ and ‘deep’ colours are consequently situated either slightly below or beyond this peak.
Out of the eight ‘chromatic’ hues, six are primary spectral hues which are red, orange, yellow, green, blue and violet, and two are modified spectral hues, these being purple and pink. Since brown, grey, black and white are not part of the colour spectrum they are not really considered as hues, however sometimes may be referred to as ‘achromatic’.
A diamond’s characteristic colour and the relative ‘warmth’ of its hue set the boundaries when it comes creating attractive colour arrangements such as colour gradations or either contrasting or matching colour sets and arrangements respectively. The best complimentary (contrasting) colours are orange and yellow in the case of Blue, green and yellow for Pink, blue and violet for Yellow and lastly green and purple for red. These colours are further reinforced via the use of appropriately coloured precious metal alloys. Red gold, for example, will pump up the colour of pink diamonds whereas a 24ct yellow gold backing would be a wise choice to frame fancy yellow diamonds with.