Worths Diamonds

Colour is critical, but it can also be confusing. Usually the more colourless a diamond, the greater the value. Depending on its size, one single increase in colour grade could boost its value by thousands of dollars. But when it shows tinges of yellow or brown, the value drops.

Yet diamonds in vivid colours (known as "fancy") are prized by collectors

Bright yellow "canary" and glorious pastel pink and blue diamonds bring big prices. Red diamonds exist too, but it’s been suggested that there are more fingers on one hand than there are red diamonds in the world.

Essentially there are three categories of diamond: white diamonds, fancy natural coloured diamonds (beautiful rarities reserved for special pieces and one-of-a-kind designs) and irradiated diamonds (stones whose fancy colours have been helped by nuclear science).

Many of the fancy colours are mined right here in Australia. There are pastel tints to purplish and champagnes, from light browns to cognac.

Generally, these stones are fairly small and are used in fashion jewellery rather than engagement rings. Often, the pinks are set in pink gold, which enhances their warmth. The champagnes are often contrasted with white diamonds to underscore their unique colour.

For an engagement ring or pendant, your goal is probably to find one that is the whitest of white. Of the Famous Four C's of diamond valuation, many experts cite colour as the prime consideration. Diamond colours are graded on a simple system, beginning with 'D' for colourless and moving down the alphabet to stones with traces of colour to stones with visible shadings. By the time you reach the second half of the alphabet (M-Z), you've found stones with poor colour.

Colourlessness is desirable because the whiter the colour, the better the diamond's ability to reflect and refract light. When white light enters the diamond, part of the ray is reflected back to the observer's eye, but the rest penetrates the stone. Refraction happens when the ray is deflected toward the centre of the stone then bounced back to the surface. The whiter the colour, the better the reaction...and that is what fire and brilliance are all about!

Because colour differences can be so subtle, they are impossible for the untrained eye to pick.

The best way to judge a diamond's colour is against a white background. To grade a diamond, gemologists often place it next to another diamond that has been previously graded. As important as colour can be, the other C's must play their part. A top colour grading of "D" means much less if the cut is poor or the stone is small.