How to Choose a Diamond

Winsor Bishop Diamond Rings


Most diamonds appear colourless or "white" but many display hints of colour by the presence of other elements during the stone's formation. These are extremely subtle shades and may go unnoticed with the naked eye. Diamonds are graded by colour and all major international laboratories have agreed 23 colour grades. Only 3 of these are classified as colourless. The closer a diamond approaches colourless, the rarer and more valuable it becomes. Diamonds with a strong, pure colour are also extremely rare and called "Fancies". Amongst these diamonds can be found the colours of pink, blue, yellow, green, orange and even black.


Diamonds have distinguishing features called 'inclusions', these develop during the stone's formation. It is normal for minute crystals, clouds and feathering to be found in most stones, even if they are only visible through a microscope. This is all part of a diamond's individual nature.The clarity of a diamond is also graded by international standard, of which there are seven categories. The number, type, colour, size and position of these 'birthmarks' determine a diamond's value. The fewer and less disturbing the inclusions, the more valuable the diamond. Only a gem free from these internal and external inclusions can be graded as 'flawless' and these are extremely rare.

Carat Weight

The weight or size of a diamond is the characteristic that most people believe is how you should measure its value – this is not strictly the case. Two diamonds of equal size can have very different values, depending on the nature of the cut, clarity and their colour. One carat weight is equal to one-fifth of a gramme and is divided into 100 point increments. So for example, if a diamond is marked as 0.75ct, this means that it is ¾ of a carat in weight or 75 points.


There are many different shaped diamonds available. However, six of these are the most popular.

  • Brilliant or round cut
  • Oval cut
  • Marquise cut
  • Pear cut
  • Emerald cut
  • Princess or Radiant cut

The shape of a diamond is largely a matter of personal preference and will not affect its intrinsic value. How a diamond is cut is by far the most important consideration. In the hands of a master craft's man, a diamond will make the most of the light, giving it a dazzling brilliance. If perfectly cut, light entering the diamond will be refracted internally from facet to facet before emerging through the top of the stone, producing a dazzling "fire" that is unmatched by any other gemstone.