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Diamonds

diamond ring 

The word diamond comes from the ancient Greek word ‘adamas’ which means unbreakable. Due to its incredible hardness and the way it disperses light it is very much sought after for use in jewellery.

The earliest known use of diamonds dates back to around 4000BC, where they were traded in India, a millennium later in the same country, they were used for engraving as well as for ornamental uses.

Natural diamonds are created deep underground where the intense heat and pressure found around 170km below your feet convert carbon into a crystalline lattice. Due to the way this lattice is formed, there are only few impurities that can contaminate the stone. Nitrogen and boron are able to enter the lattice in very small numbers (around 1 part per million) and create colour in the otherwise crystal clear gemstone.

Blue diamonds contain traces of boron and yellow diamonds have nitrogen present. Brown diamonds are given their colour by having defects in the lattice, rather than impurities being present. Diamonds are typically brought to the earth’s surface due to volcanic activity, but most volcanoes don’t reach the depths where diamonds are created, the source of the magma for most volcanoes is only 50km below the surface of our planet.

Diamonds for gemmological purposes (jewellery) are graded on four factors. Carat, Colour, Clarity and Cut, so diamonds with similar ratings will be expected to be priced closely together.

Carat is a weight measure of the mass of a diamond. One carat is 0.2 grams or 200 milligrams. The majority of diamonds are below 1 carat in weight and are measured in ‘points’. One point is 1/100th of a carat or 2 milligrams.
With all other factors being equal, the price of diamonds is not linear. In other words, a 10 point diamond will not cost 10 times more than a 1 point diamond, it will cost more.

Certain ‘milestone’ carat weights also play a part in the price of these stones. A 0.98 carat stone may be substantially cheaper per carat, than a similar gem weighing 1.03 carats.

Total Carat Weight (TCW) is often used to state the weight of all stones in a piece of jewellery. This can be quite misleading (in terms of value) as a single one carat stone will be considerably more expensive than 10 stones with a total carat weight of one carat.

Clarity refers to the internal defects (inclusions) that are present in nearly all diamonds. These inclusions come in several forms including tiny cracks in the crystal, impurities of another material or even another diamond crystal within the diamond. The overall clarity of a diamond is affected by the size, colour, relative position and the visibility of these inclusions.

Approximately 80% of all the diamonds mined have a clarity that precludes their use in jewellery and become ‘industrial’ diamonds. Of the 20% remaining a high proportion have one or more inclusions that are visible to the naked eye. Those that don’t are referred to as ‘eye clean’ and are the preference of most buyers.

An experienced grader views the stones under 10x magnification and will assign a clarity rating on a scale ranging from flawless to included.

FL   Flawless
IF   Internally Flawless
VVS1, VVS2   Very Very Slightly Included (VVS1 is a higher grade than VVS2)
VS1, VS2   Very Slightly Included
Sl1, Sl2   Slightly Included
I1, I2, I3   Included

Colour of white stones is graded on a scale from ‘D’ being totally colourless through to ‘Z’ being light yellow. The broad ratings of D, E & F are colourless, G, H, I & J are near colourless, K, L & M are faint yellow, N, O, P, Q & R are very light yellow and S through to Z are light yellow.

The colour of a diamond can have a profound effect on its value. As white diamonds tend towards a yellow tint, their value decreases; except for very yellow as is the case with blue or pink diamonds, a higher intensity of colour can dramatically increase their value.

  Cut is the manner in which a rough stone is shaped and polished into the proportions of a finished gemstone. It is not the shape of the stone. It is both an art and a science and requires a highly skilled person to achieve the best result from a rough stone.

Some of the larger rough diamonds with a huge potential value are studied for more than a year to determine the optimum cut. Urban legend has Joseph Asscher fainting after striking the Cullinan Diamond (3,106 carats) to split it into the 9 stones that would eventually take pride of place in the crown jewels of Great Britain.

The modern round brilliant cut was developed by Marcel Tolkowsky, a mathematician in 1919. It is the ideal shape to show off a diamonds brilliance when viewed from above. There are 57 facets in all, 33 on the top half (the crown) and 24 on the lower half (the pavilion). The middle of the stone is called the girdle and was introduced to reduce the chance of a diamond being damaged in its setting. The bottom of the stone is known as the culet.

The shape of a stone will determine how much lustre, fire and brilliance are produced. Any diamonds not cut into a round brilliant shape are called fancy cuts and these include the princess, marquise, baguette, heart, pear and briolette.

These cuts are often dictated by fashion trends with the baguette achieving popularity during the art deco period and in recent times the princess cut has become common. The princess cut also lets the cutter maintain the highest percentage of the rough stone.
 

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