Diamond grading is a serious business. Most people know that diamonds are graded use the four C's - colour, cut, clarity and carat weight - but in addition to these classifications, there are additional factors that affect a diamond's appearance and price.
All three of these diamonds have a GIA certificate that classifies them as the same cut, colour, clarity and carat weight but they are clearly not all the same.
A person who grades diamonds is a gemologist, which is someone trained in the science of gemology. Diamond grading aims to take a natural material and classify it into specific categories in order to assess the value. As each diamond is unique, it's a very tricky thing to do and requires years of experience as well as training. Not only is it a very skilled job, it is also subjective and so one diamond grader's opinion may vary from another's.
For this reason, many people prefer to buy diamonds which have been independently graded by a laboratory which is not involved in the direct sale of the stones. There are several laboratories around the world but the two most highly respected ones are the GIA (Gemological Institute of America) and the HRD (the diamond high council based in Antwerp)
Diamonds which have been independently graded by these organisations come with a certificate that explains the different features of that particular diamond. The diamond is also marked with a unique number that can only be read using a microscope.
The grades of a diamond affect the price enormously. For example today, you could buy a 1 carat diamond with the same colour, cut, clarity and carat weight and pay from £4000 to over £8000 depending on the other factors that affect the price of the stone.
So how do you know what to look for in a diamond and how do you know that you are paying the right price for it?
When I buy diamonds, I only purchase from trusted sources. Every diamond trader we use has signed up to the Kimberley Process. The KP unites 81 countries around the world and traces the source of the diamond from the mine to the consumer, In addition to this, I purchase using the Rapaport list. Diamonds are priced on an index called RAP. This index traces the worldwide demand for diamonds so that prices for stones are led by supply and demand rather than fixed by the people who trade them. This means I can be sure that I am not over paying for diamonds.
I understand how to read a diamond certificate which gives me a good idea of what the stone will look like before I buy it but I would never buy a diamond just from a certificate. A diamond needs to be viewed with the eye to know the full story of what that stone is like. The dealers I trade with supply me stones on approbation, which means I can look at them and return them without paying for them if they don't live up to my expectations.
When I start to look for a particular stone, I consider lots of factors. I scan through hundreds, sometimes thousands of individual stone certificates looking for a diamond that has exceptional visual qualities and which will also be great value for money. It's important to remember with diamonds that tiny, sometimes visually imperceptable differences can affect the price. The skill in buying a diamond is not to pick the stone with the highest grade, but to pick the best looking stone for the money.
When customers come to me looking for a diamond ring commission, I'm able to show them a selection of diamonds in different grades with a variety of prices so that they can make their own minds up about how much they'd like to spend. Being shown the differences between the diamond grades with the stones can be really eye opening and customers can be surprised, and delighted, that they actually prefer the diamond that costs less.
Gemology is a science but grading is also an art because it is subjective. What one person sees with their eyes is different to what another does. That's why I think buying a diamond where you can see a selection of them together is the best way to get the right diamond for you.