The Four C’s: FOUR CHARACTERISTICS TO HELP YOU ASSESS YOUR DIAMONDS 

info found at christies.com januari 2008

• There are many different diamond cuts, and amongst the classics are round brilliant, oval, marquise, pear, heart and rectangular step-cut. The shape of a diamond is often determined by the original crystal form, in order to maximise the weight. For example, a flat, tabular shaped crystal could be polished to become a rectangular step-cut diamond (also known as the emerald-cut). 

• Round brilliant-cut diamonds are the most sought-after and expensive because they are the most ‘wasteful’ in terms of how much material is lost from the original crystal. This is also the cut that reflects the most light, giving the ‘sparkle’, or brilliance. 

• Antique diamond cuts are increasing in popularity and although they often don’t meet modern ideals for proportions they have a unique subtlety and elegance. 

1.Cut

 • The most desirable colour is ironically the diamond without colour, the most expensive being the rare whites, from D to G colour (D being the whitest). Grades H to Z show progressively more colour (often yellow), and this is much more obvious to the eye from M onwards. It is easier to grade the colour of a diamond from the side of the stone, although this can be more difficult when it is mounted.

 • When diamonds are classed as ‘fancy coloured’, a different grading system is used. 

2.Colour 

• Clarity is based on the combination of internal flaws (inclusions) and external features. Inclusions can be other materials that crystallised at the same time as the diamond or natural characteristics due to the crystallography of the stone. On the outside of the diamond there can be other natural features. A diamond without inclusions of any kind is known as flawless. 

• The standard tool for grading diamonds is a 10x lens and we would advise you to sweep your eye around the stone as a minute hand might a clock face, therefore scanning the whole in a systematic way. 

3.Clarity 

 • Clarity is based on the combination of internal flaws (inclusions) and external features. Inclusions can be other materials that crystallised at the same time as the diamond or natural characteristics due to the crystallography of the stone. On the outside of the diamond there can be other natural features. A diamond without inclusions of any kind is known as flawless.

• The standard tool for grading diamonds is a 10x lens and we would advise you to sweep your eye around the stone as a minute hand might a clock face, therefore scanning the whole in a systematic way.

3.Carat

• The name ‘carat’ is derived from the name of the carob or locust tree, the dried seeds of which were once used by traders as a unit of weight. 

• Pricing of diamonds goes up in steps between whole carat sizes.