...diamonds are one of the worlds most important mineral resources, formed from pure natural carbon with the atoms organised in a close-packed cubic arrangement that gives them their hardness.

They are the hardest of all gemstones and the hardest transparent substance known to man. They are formed by extremely high pressure and temperature and found in 'Kimberlite' or 'Lamproite' pipes produced by volcanic magma, millions of years ago.

Because of their hardness they make ideal Gemstones, and also have many industrial uses.

A rough diamond resembles a common pebble, but properly cut and polished, they come to life with their 'fire' or brilliance. The magnificent optic properties are caused firstly by their high refractive index (2.417 if you really want to know), or light bending ability, this allows it to throw back almost all of the light which enters it, giving it's lustre.

Fewer than 20% of the diamonds mined each year are suitable for use as Gemstones.

Four factors are used to determine quality:

• Carat Weight
• Cut
• Clarity
• Colour

Carat Weight...

...one Carat = 0.2grams, one Carat is also = 100 points, so a 50 point diamond is described as 0.50 Carats.

Cut...

...how well the diamond has been cut. The cut of the diamond gives it a unique sparkle or brilliance by allowing the maximum amount of light to enter and be reflected back. There are six different shapes to which a diamond is cut, round brilliant cut diamonds account for more than 75% of all diamonds sold, the other cuts are marquise,pear shaped,  emerald-cut, oval and heart shaped:

Clarity...

...defined by how flawless the diamond is. Flaws consist of natural phenomena known as inclusions such as scratches, impurities, cracks and non-crystallised carbon.

The following shows the standard gradings used for clarity:

• Flawless (F) - No inclusions or blemishes seen under 10X magnification.

• Very, Very Slightly Included (VVS1/VVS2) - minute inclusions that are difficult to see under 10X magnification.

• Very Slightly Included (VS1/VS2) - Inclusions are clearly seen but minor and small.

• Slightly Included (SI1/SI2) - Inclusions are noticeable and fairly easy to see under 10X magnification but not noticeable to the unaided eye.

• Imperfect (I1/I2/I3) - Inclusions that are obvious under 10X magnification or can be seen with the naked eye.

Colour...

...Grading standards for colour range from D to Z as shown below, with Grades of D to H being preferred for fine jewellery. The value of the diamond decreases as you progress down the scale:

The market value of a diamond is a combination of these four factors with hundreds of possible combinations, the current trend is to give high priority to colour, then clarity, then cut and finally to carat weight.