A guide to buying diamonds…

Investing in ‘a girl’s best friend’ and joining the league of believers in the ‘diamonds are forever’ club is an exciting prospect first and foremost, but then probably daunting is the next word that will spring to mind and then perhaps sheer panic may just set in!

Whether it is a special birthday or anniversary gift, a well earned treat, an inheritance investment or your engagement ring, you want to get it right. But where do you start? Are you choosing it for yourself or is it a ‘no pressure here’ but you’re picking a surprise for the love of your life? What can I tell you here that will ensure you leave home armed with the knowledge necessary to bag some blinding bling and come home with your perfect diamond to show off, share and wear with confidence, and love it?

It’s all about you! That is the top and bottom of it – and whilst I will give you an idea of the ‘technical’ side of things at the bottom of this page, when it comes to down to the crunch, it must be right for you and only you know if it makes you sparkle as much as the piece itself does!

There are the folks out there who take the impulse approach (not unlike myself) who will see it, love it and get it there and then; because if you go back and it’s gone you will totally kick yourself! 

Then there are the folks who are far more measured, who may see something they quite like, yet when they pass by a few weeks later and it’s gone, that’s fine, it just wasn’t meant to be and they’re in no hurry. 

Probably the best place to start is with your budget. What is it? This is the key to determining how far you can push that proverbial boat out. It is definitely possible to bag a pre-owned gem that will give you the look of a champagne lifestyle on a lemonade budget, if that’s what you’re after! So set a budget and work from that.

Pennies sorted, occasion determined, next thoughts are probably on styles, traditional, unusual, simple, statement? Start by looking at everything and narrow it down from there! You’ll potentially be surprised by what catches your eye and I always believe you will ‘know it when you see it’, personally I can hear things (mainly shoes and diamonds) calling my name, but this is the FUN bit, the thrill of the chase, so happy shopping!!!

The 5 C’s to know a bit more about are:
Cut, Clarity, Colour, Carat & Certificate


There are many styles of ‘cut’ including, brilliant (your standard modern round diamond), oval, princess, heart, marquise, pear, emerald, baguette, old European, rose, dutch rose…..

This is certainly a personal preference on what shape you feel suits you best……. Unless you are grading the diamond as an expert and then the ‘cut’ is a grade of the diamond’s reflective qualities, not the shape at all!

The quality of the cut does affect how the diamond looks, the brilliance or fire that comes from within, the finish and the angles of the cut determine how well the diamond handles the light. If you are looking at a certified diamond then if it states the ‘cut’ these are key words you will come across: ideal, excellent, very good, good, fair & poor. Ideal is the best, scaling down from there…..confused yet?

We are still only on the first ‘C’ and I saved you the lecture on the ‘anatomy’ of a diamond!!


So this is all about the flaws, inclusions, black speckles, air bubbles and ‘stuff’ that is found in non flawless stones. I will keep this simple; it goes on a sliding scale again as follows:

F: Flawless: everyone wants one, only the very rich and famous can potentially get their hands on one!!

IF: Internally Flawless: No flaws internally, but some surface flaws. Still rare!

VVS1 / VVS2: Very Very Slightly Included 1 & 2 (1 is better than 2): These have minute inclusions that are very difficult to detect under a loupe (with 10x magnification) even by a trained gemologist. Readily available for sale.

VS1 / VS2: Very Slightly Included 1 & 2: These have minute inclusions seen only with difficulty under a loupe at 10x magnification. Much easier to find for sale.

SI1 / SI2: Slightly Included 1 & 2: Minute inclusions, visible under a loupe at 10x magnification and may be visible to the unaided eye. Readily available for sale.

I1 / I2 / I3: Included 1, 2 & 3: Inclusions visible under a loupe at 10 x magnification; and visible to the naked eye.
What clarity diamond should you buy?

Well the higher the grade the better (and more expensive) the stone as described above. But, it needs to be in budget and who in the real world walks around with a loupe in their pocket all day to let people examine their diamonds when showing them off? No, not me either!


Diamonds are white, yes. But ‘fancy’ diamonds can be pink, red, blue, yellow, green etc. White diamonds are measured in colour on a scale from D – Z and all D-Z diamonds are considered white, even though they contain varying degrees of colour. True fancy coloured diamonds are graded on a separate colour scale. The whiter the diamond the more valuable and the better the look, if you have a colourless diamond you will do it no favours having it set in yellow gold instead of white gold or platinum as the yellow gold will reflect colour, negating the diamonds colourless effect. That said, a slightly yellow diamond will appear whiter in a yellow setting, so the eye can be deceived!

D E F      Colourless. There are differences between these 3 grades, but a gemologist will need to use side by side comparisons to detect them.

G H I J   Near Colourless. Containing traces of colour these stones are still suitable for white settings.

K L M     Faint Yellow. These stones are where colour becomes more apparent to the naked eye.

N – R     Very Light Colour. An easily seen yellow to brown tint.

S – Z       Light colour. Most people will think there is too much of a tint in yellow to brown to buy a stone of this grade.


The carat is not, as commonly misconceived, relating to the size of the stone, but the actual weight of the stone.

Which is ‘fun’ because then you have the carat of gold too, which is the purity of the metal, so a ring can have 18 carats and a quarter carat at the same time and confuse the best of you before you’re started!

1 carat is equal to 0.2 grams, but pre-owned and in it’s original vintage setting you will most likely be buying an ‘approximate’ weight stone and as the cost and disturbance to the piece to unset, weigh and reset is probably not cost effective and could be detrimental.

However, a general rule of thumb can give a ‘size’ guide. So for example 4.1mm is perceived as a ¼ carat, 5.1mm a ½ carat, 6.4mm a full carat, 8.1mm for 2 carats and 11mm for 5 carats. Shallow stones can appear ‘bigger’ than they actually are and deeper old cut stones for example may look ‘smaller’ than they actually are in a type of iceberg effect!

The smaller the carat the cheaper the stone, and so a cluster of many diamonds totalling 1 carat can look big and impressive but for a fraction of the cost of a single stone with the same carat content, it’s definitely down to personal preference (and budget) again!


A certificate is a blueprint of just your stone, (not the mount or metal that it is set in) telling you about the four C’s as above, essentially the stone’s exact colour, clarity, cut and carat credentials, as no two diamonds are the same it is like a passport almost. 

But a certificate does not value the stone. That is called an appraisal or valuation. Fantastic to have both a valuation and a stone certificate, but highly unlikely in most cases involving vintage or second hand jewellery as papers can sadly be lost along the lifetime of ownership or just may not have been present in the first place.

In pre-owned terms although it is rare that pieces come with certificates, it is more likely to be accompanied by a replacement valuation (for insurance purposes for example) of the piece as a whole. This valuation document can include lots of information including an experts approximation of the cut, colour, clarity and carat of any stones set in the piece. See our jewellery valuations page for further information on what we can / do provide.