Diamond Facts

Diamonds are the purest of all gemstones as they are composed of a single element. They are also the hardest substance known to humankind, and are made of crystallised carbon with unique powers of light reflection. Discovered in India around 500 BC, the name 'diamond' originates from the Greek 'adamas' which means 'unconquerable'. From ancient Greek times, diamonds have been the traditional symbol of love and many believed they were hardened dew drops, splinters from the stars or crystallised lightening. Today the diamond is the gemstone for the 10th and 60th wedding anniversaries, and the birthstone for the month of April.

THE STRUCTURE OF A DIAMOND

Proportion is the term given to the angles and measurements of a polished diamond. It is these 'proportions' that determine the optical properties of the diamond, and studies have shown that pavilion depth, crown angle, and table size have a huge effect on a diamond's appearance. Symmetry is the term given to describe the accuracy of shape and placement of facets. Variations in the symmetry can include poor facet alignment, off centre culets and tables, misshapen facets and out of round or wavy girdles.

Reflection A) When a ray of light touches the surface of a diamond, part of the light is reflected back. This is external reflection.

Refraction B) The rest of the ray penetrates the stone and is then reflected toward the center of the diamond. This is known as refraction.

THE VALUE OF A DIAMOND: THE FOUR Cs

Shape (Cut)

The brilliance of a diamond is dependent on the cut. Quality diamonds must be professionally cut, and not 'spread'. 'Spreading' is an improper practice which compromises the proper proportions of the diamond to make it increase in weight. A classic round, brilliant cut diamond has 58 facets – 33 on the top, 24 on the bottom, and the culet which is 1 point at the bottom. Every one of these facets has to be placed in exact geometric relation to the next when the stone is being cut.

Clarity

The clarity of the diamond depends on the number, size and location of inclusions found in the stone. Under the magnification of a jeweller's loupe, imperfections or trace minerals can be seen in the stone. These are called 'inclusions'. The diamond will increase in value when there are fewer inclusions present, and will be clearer and more brilliant. A diamond with no inclusions is extremely rare and valuable, and is given the term 'flawless'.

Colour

When viewed under a jeweller's loupe, most diamonds contain slight traces of light brown or yellow pigment. Colourless and near colourless diamonds are much more valuable, and taking the stone's size into consideration, a single increase in colour grade can raise the value of a diamond by thousands of pounds per carat. Engagement rings traditionally use diamonds that are colourless, or near colourless.

Naturally, diamonds can be found in shades of blue, green, red, pink and deep yellow. These are known as 'fancy diamonds'. Worldwide, colourless diamonds are graded using an alphabetical scale. Colourless or 'rare white' diamonds are graded D,E and F, the most valuable being the D grade, which is extremely rare.

Carat Weight

Judging a diamond on the carat weight alone can be very misleading. The cut, clarity and colour of the diamond are extremely important and have to be taken into account. A large stone will not generally be valuable if it lacks purity, high grade colour and brilliance. However, as larger stones are rarer than smaller ones, the value will rise exponentially with carat weight, making a 3.0 carat diamond worth more than three 1.0 carat diamonds of equal quality. So, when making your decision as to which diamond to buy, take all these factors into account – colour, clarity, carat weight and cut.