How to buy a diamond

How to buy a diamond

8 tips

8 Tips

How to buy a diamond

Diamonds are forever, as the saying goes. To find out how to best go about buying a sparkly piece of forever we talked to Annemieke Jansen, commercial director of Royal Coster Diamonds. The oldest diamond polishing factory in the world has been in business since 1840 and still have their own cutters and setters working at the premises. Jansen has been with Coster Diamonds for over 50 years so it’s fair to say she knows a thing or two about diamonds.


1. You don’t have to be rich (although it helps)

Maybe the biggest misconception about diamonds is that they are (too) expensive. Granted, they are not cheap, but there is a diamond to fit nearly every budget. Plus, as Jansen explains: ‘If you buy a new car, the minute you drive away its value is already decreased. A diamond keeps its value. And if for example you buy a € 1000 euro diamond from us and want to exchange it for a more valuable piece after a few years, we will return the exact same amount of the original to you.’


2. Mind the four C’s

To determine the value of a diamond there are 4 important factors, known as the four Cs.


The weight measured in carats. One carat equals 200 mg and is subdivided into 100 points. Two diamonds weighing exactly the same can still vary in price though, because of the other Cs. 


Because of the way they are formed within the earth diamonds may have imperfections (called inclusions and blemishes) which have an effect on the brilliance and transparency. Diamonds are graded for clarity using an 11 point scale. Jansen: ‘It’s okay to purchase a lesser quality as long as you know what you’re buying. We would advise not to go for the lowest grade though, as these imperfections can be visible to the naked eye.’


A chemically pure and structurally perfect diamond is like a drop of pure water and higher in value than a white diamond with a yellowish tint to it. This is because the less colour it contains, the more colour it will reflect. Colour becomes more important as carat weight increases because it is easier to perceive in a larger diamond.


A diamond’s cut is not about the shape (round, square, pear etc.) but how well its facets interact with the light and it is crucial to its final beauty and value.


Jansen: ‘I always joke that people should not forget about the important 5th C: for Coster Diamonds!’

3. Size matters…

The bigger the weight of the stone, the more valuable it usually is. But as we learned from the 4 Cs, weight is not the only factor contributing to the value of a diamond. But if a big stone is what you like, picking one of lesser quality can cost significantly less and some of the imperfections which make it cheaper are not visible if you are not an expert with a magnifying glass.

4 …But shape doesn’t

From pear-shaped to the square princess cut or the romantic heart shape, it doesn’t matter what takes your fancy. Where weight, clarity, colour and cut determine the value of the diamond, shape is a matter of personal taste. If you want an original ‘Amsterdam’ cut though, why not go for the Royal 201 – with a staggering 201 facets - which was exclusively developed by Coster Diamonds.

5. Pick a colour

In normal ‘white’ diamonds, value is determined by the absence of colour, but with coloured ‘fancy’ diamonds the rarest colours, like pink, blue and green are the most valuable. The most common fancy colours are brown and yellow.

6. Go to a reputable diamond firm or jeweller

This may sound obvious, but  there are still people who are conned because they think they are getting a good deal. Jansen: ‘Our diamonds come with an international certificate of authenticity stating the specifications of the diamond, like the weight. It so sad sometimes when people come in here to have their diamonds valued and they have been cheated by some untrustworthy dealer.’


7. Take care of your jewellery

Jansen: ‘If you buy a piece of jewellery with us, come in every year to have it checked and cleaned. Whereas the diamond itself is rock-hard, the setting may not be, and if there is some unnoticed damage, you might lose the stone altogether.’


8. A diamond is forever

Don’t worry about fashion trends when it comes to diamonds. Just buy what you like because you can always have the stone reset if you don’t like the original. Trends come and go, whereas diamonds are indeed forever.


To find out more about diamonds and see the cutters at work or indeed, purchase a diamond, you can book a free guided tour of Royal Coster Diamonds or visit the Diamantmuseum.