Diamonds are essentially carbon formed in a particular crystal lattice structure. They constitute the hardest substance on Earth. Gem-quality samples of this crystal can be cut with expertly placed diamond facets: the smooth areas that reflect and refract light, creating brilliance and lustre.

WHERE DO DIAMONDS COME FROM?

All but the tiniest of diamonds are formed way below the Earth’s crust, over billions of years and under very high pressure. Ancient volcanic eruptions brought diamond-bearing rock to the surface up along volcanic pipes extending 100 to 200 miles down. The rock containing the diamonds then gets dispersed and eroded, enabling the diamonds to be mined.

Very tiny diamonds can be formed when meteors impact on the Earth’s surface.

Black diamonds are formed differently. There are several theories about this.  One fascinating one is that they are created during supernovae explosions and then transported to Earth via asteroids.

WHAT MAKES A DIAMOND EXPENSIVE?

Four aspects, sometimes known as the ‘four Cs’ contribute to the value of any gem-quality diamond: carat, cut, colour and clarity.

Carat weight: this measures the mass of a diamond. One carat is defined as 200 milligrams.

Clarity: this is a measure of the internal defects of a diamond, called ‘inclusions’. Inclusions may be crystals of a different material or another diamond, or imperfections such as tiny cracks. The number, size, colour, position and visibility of inclusions can all affect the clarity of a diamond.

Colour: a chemically pure and structurally perfect diamond is completely transparent with no hue. In reality, most gem-sized natural diamonds are imperfect. The colour of a diamond may be affected by chemical impurities or structural defects in the crystal lattice. The hue and intensity of a diamond’s coloration can really affect its value. The most prized grading is ‘D’, meaning that it is absolutely free from any colour.  The more white diamonds have a yellow hue, the more they diminish in price. But intense pink or blue diamonds can be dramatically more valuable.

Cut: the cut of a diamond is the manner in which a diamond has been shaped and polished from its original form to its final gem proportions. Part of the skill is to obviate any imperfections. The cut describes the quality of workmanship and the angles to which a diamond has been cut and faceted.

WHAT IS THE MOST EXPENSIVE DIAMOND?

It is hard to say which diamond is the most expensive, because information is not available on the appraisal value of some of the world’s most evidently expensive diamonds.

The Golden Jubilee, at 545.67 carats (109.13 g), is the largest faceted diamond in the world. It was discovered in 1985.

The Cullinan Diamond was the largest rough gem-quality diamond ever found. The largest polished gem from the stone is the ‘Cullinan I’ or ‘Great Star of Africa’ and weighs 530.4 carats. The second largest is the Cullinan II or the ‘Lesser Star of Africa’, At 317.4 carats (63.5 g) this weighs in as the world’s fourth largest polished diamond.

The 968.9 carat (193.8 g) ‘Star of Sierra Leone’ was discovered in 1972.It ranks as the third largest gem-quality diamond and the largest alluvial diamond ever discovered.

The Incomparable Diamond, a brownish-yellow diamond of apparently flawless clarity, weighs in at 407.48 carats (81.496 g). It was cut from a 890 carat (178 g) rough diamond of the same name. The Incomparable appeared on eBay in 2002.

The Centenary Diamond weighed 599 carats when it was discovered. Its cut weight is 273.85 carats.  It was cut into modified heart-shaped ‘brilliant’. It is the world’s largest colourless Grade D flawless diamond. In 1991 it was insured for over $100 million.

WHAT TYPES OF DIAMONDS ARE THERE?

When choosing a diamond and considering the four C’s, we want especially to consider the shape into which the diamond has been cut and polished. There are generally speaking nine available types or ‘cuts’.

Round Brilliant Diamonds

These days three-quarters of available diamonds are Round Brilliants. The 58-facet cut is calibrated to a precise formula to ensure fiery brilliance.

Oval Brilliant Diamonds

The long, symmetrical shape of the Oval has the brilliance of the Round, but can also help to accentuate long, slender fingers. Oval Brilliants were first created in the 1950s by the diamond company, Lazare Kaplan.

Marquise Diamonds

The Marquise has an elongated shape with pointed ends. The name is derived from Louis XV’s instruction to his jeweller to cut a gemstone to the shape of the mouth of his mistress, the Marquise de Pompadour. A Marquise looks good either as a solitaire or surrounded by smaller diamonds.

Pear Shaped Diamonds

Shaped like a glistening tear-drop, the Pear Shaped combines the advantages of the Oval and the Marquise. To determine the most pleasing proportions for a Pear Shaped, look for a length-to-width ratio of between 1.50 and 1.75:1.

Heart Shaped Diamonds

This is a very romantic style, but the Heart Shaped is essentially a Pear Shaped with a cleft at the top. Choose a stone with an even shape and a well-defined outline.

Princess Cut Diamonds

The Princess cut is a square cut with numerous facets. It’s a modern innovation quite often used in engagement rings. In choosing a Princess Cut in a ring, ensure that the setting covers the corners to avoid the chipping of the stone.

Emerald Cut Diamonds

The long, rectangular lines of this cut, as the name suggests, were originally used on emeralds. The result is less of the fiery lustre than the Round Brilliant, but instead broader, more dramatic flashes of light.

Radiant Cut Diamonds

The Radiant is a square or rectangular cut combining the elegance of the Emerald Cut with the brilliance of the Round. It has 70 facets, which maximize the colour refraction of the stone.

Asscher Cut Diamonds

This cut harks back to the design created by the Asscher Brothers in Holland in 1902. It is a square Emerald Cut with rounded corners. The style has regained popularity since Kate Hudson and Liz Hurley have been seen with Asscher Cut diamonds.