Because diamonds are so valuable, it's important to have a universal grading system to compare their quality. In the 1940s and 50s, GIA developed the 4Cs and the GIA International Diamond Grading System™ to objectively compare and evaluate diamonds.

CUT

The only diamond characteristic within human control is the cut. It is extremely important. The ideal proportions of the stone reflect light back to the eye and give it the famous "diamond" sparkle.

The most common cut is the round brilliant cut and a diamond cut in this way is called a "brilliant". A diamond loses about half of its original weight when cut. There are a few other standard shapes: Princess, Emerald, Marquise, Oval, Heart, Pear, Baguette, etc.

     

 

 

COLOUR

It is the absence of colour that makes a diamond most valuable.

Diamonds are the only gemstone that can be found in all the colours of the spectrum. Although diamonds are thought to be colourless, they have a mixture of yellow, grey and brown. The most valuable are the backs. These are colourless or "fancy colour" diamonds: pink, blue, yellow and red.

There are also black diamonds. GIA has classified diamonds according to a colour grading scale that starts with the letter D (colourless) and ends with Z (yellow).

Colour determination is a very complex process and must be carried out under certain specific conditions, making it impossible to determine the colour of a stone already set in jewellery due to metal reflection.

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CARAT

A carat is the weight of a diamond. One carat equals 0.20g.

The carat price of a diamond increases progressively with the size of the stone. Larger diamonds are rarer. In other words, one carat diamond is more valuable than 100 tiny diamonds of 0.01ct.

CT	0.01	0.05	0.10	0.15	0.20	0.25	0.33	0.50	0.75	1.00	1.25	1.50	2.00	2.50
MM	1.50	2.25	3.00	3.40	3.70	4.00	4.50	5.00	5.90	6.50	7.00	7.50	8.00	8.50

CLARITY

There are often some internal features called inclusions (dark "carbon", white "ice", cracks, etc.) that have been created during certain stages of diamond formation.