The term 'colour' can be misleading when referring to diamonds, as the optimum stones are actually characterised by a lack of colour. Therefore the ideal stone would be clear or colour-less. This is because the colour found in diamond is a result of impurities within the stone. The slightest variant of colour, undetectable by the untrained eye may affect the ultimate value of the stone by thousands of pounds.

The highly skilled task of assessing colour within diamonds is performed using a master set of comparison stones whose official colour grades are known. Colour grading is defined using the alphabet ranging from D to Z. The absence of Grades A, B and C is owing to the possibility of purer stones being un-earthed one day.

It is also worth mentioning that diamonds possessing intense colour fall in to their own classifications and can come in at a high premium if the colour is natural. These stones are referred to as 'fancies'.

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