A diamonds cut, also the most important C, refers to its proportions and finish, influencing the value of a diamond. The way it is cut is the only factor that we have a say in, as it is not determined by nature. 

The cut should not be confused with shape, which refers to the shape of the finished diamond, such as princess or baguette.

The cut of the diamond can affect the way the light catches the stone, effecting the way it sparkles. The way a diamond is cut affects three important diamond-attributes:

• Brilliance – the total light reflected from a diamond
• Fire – the dispersion of light into the colours of the spectrum
• Scintillation – the flashes of light, or sparkle, when a diamond is moved 

GIA (Gemological Institute of America), the most trusted name in the industry because of their strictest grading comes up with 4 cut grades: 

2. COLOR

The most desired and precious traditional 'white' diamond should be as colorless as possible. The GIA (Gemological Institute of America) defined and developed a very precise scale of color grading, and use this to grade diamonds by comparing them to a master stone. 

The scale runs alphabetically from D to Z+, with D being the highest, best grade possible given to diamonds that are the rarest and most desirable. This is the grade that is classed as colorless. The full scale runs as below:

 Remember, the higher up the alphabetical color grade, the better the color of the diamond – increasing the value.

Completely colorless diamonds are exceptionally rare. High quality commercial diamonds are most likely to fall within the G-J grading of 'near colorless.'

3. CLARITY

 Clarity refers to the level of flawlessness the diamond has. Imperfections are defined as inclusions (internal flaws), which can make the diamond look cloudy, and blemishes (external marks) such as scratches. The fewer imperfections a diamond has, the more flawless it is, meaning the diamond is considered to be rarer and more valuable.

However, bear in mind that most imperfections will be invisible to the naked eye, and perfect clarity is exceedingly rare in a diamond. Assessments are carried out under a 10x magnification, and upon this examination, a diamond will be graded for clarity against an approved scale, as was the case for colour. Inclusions may affect the brilliance or sparkle of a diamond, as it is possible they can cloud the way the light hits or bounces off the diamond.

The full GIA scale runs as below:

• FL: flawless
• IF: internally flawless
• VVS1-VVS2: very, very small inclusions
• VS1-VS2: very small inclusions
• SI1-SI2: small inclusions
• I 1-I2-I3: inclusions may be visible to the naked eye

 

4. CARAT

Carat refers to the weight of a diamond, and not the size. One carat of diamond weighs 200 milligrams and can be divided as 100 points of diamond.So 50 points of diamond refers to half a carat of diamond and 25 points refers to a quarter of a carat of diamond, and so on.

Many people consider the carat to be the main factor that determines the value of a diamond, as in many instances the bigger the diamond, the more you'd expect to pay. However, this is not the sole factor in determining a diamond's wealth, and should not be the only factor taken into account, as the other C's can have a big impact.

Two diamonds of the same carat may differ dramatically in value, if their color and clarity are extremely different. So it is important to remember to check the other factors alongside the carat, and not just assume that the higher the carat weight, the higher the value of the diamond, as this is not always the case.