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A buyer's guide to diamonds, from the UK's leading online auction house.
4 Mins

Buyer's Guide: Diamonds

Jess Gibson
Jess Gibson

Unearthed in 4th century India, diamonds have long been a coveted stone and a symbol of wealth in society - the absolute pinnacle of all gems, often mimicked yet never successfully replicated.

Via the caravans that traversed Europe in the 1400s to reach Venetian markets, the upper echelons of society were soon introduced to the limited supply of diamonds, and began adorning their clothes and accessories with the glittering stones. Once India's supply started to dwindle in the 1700s, Brazil became the next diamond epicentre when gold miners, sifting through rivers and streams for fragments of gold, discovered the gems. By the 1800s, South Africa's significant deposits were identified, just as demand amongst the European population increased following the French Revolution and widespread redistribution of wealth.

This led to diamonds being in high demand, chiefly used on necklaces and brooches as well as engagement rings (for which they are most well-known). Referred to as 'a girl's best friend', most ordinary people actually have very little specialist knowledge regarding diamonds, many assuming that bigger means better. This can be a hindrance when attempting to decide on whether to purchase a piece of diamond jewellery - especially when scouring through online auctions, where you rely on an image as opposed to the naked eye. There are, however, ways to identify the best of the best.

So, worried about losing money? Confused by the choice and language used? That's where we step in - you can use our diamond buying guide to help you find what you're looking for and make sure you're paying for something worth its salt.

Remember the 4Cs

The four most important elements of diamond assessment are the cut, colour, clarity, and carat weight of the gem. Once these characteristics have been determined, the shape and setting can then be analysed.

A misconception surrounding these precious gems is that a larger diamond carat weight equals a superior quality diamond, when, in fact, this is not quite true. Whilst a diamond's carat may have the biggest influence on price point, the cut of the diamond - which affects its sparkle - is actually a more important measure of quality.


When assessing the cut of a diamond, it's essential to look at the number of surfaces and facets, and work out how well-proportioned the dimensions are. For example, what is the ratio of the diameter and depth? These aspects affect how beautiful the diamond itself is, by influencing the refraction of light off the various surfaces and, therefore, it's level of sparkle.

Three different elements are looked at when determining the cut quality: brilliance, which refers to the reflection of white light; fire, which surrounds the dispersion of light into the colours of the rainbow; and scintillation, which is about the contrast between the play of dark and light on the diamond.

The cut is frequently used interchangeably - and incorrectly - with the shape, which causes confusion amongst consumers. The shape is the diamond's outline, whilst the cut is the performance of light on the surface, determined by the proportions, symmetry, and polish of the diamond.


In terms of colour, higher grade 'white' diamonds tend to appear as close to colourless as possible. Despite this, coloured diamonds - which are incredibly rare, with just 1 in 10000 diamonds possessing naturally-occurring colour - can also fetch substantial prices, although they're graded on a separate scale to white diamonds. The more intense the colour, the rarer it is, and therefore the more valuable it is.


The least important of all a diamond's qualities, the clarity of a diamond is related to the imperfections that exist on and inside it. Surface flaws are called blemishes, while internal defects are known as inclusions and, generally, cannot be perceived by the naked eye.

The lower importance of this element is due to the fact that the vast majority of imperfections are so small that they can only be seen via a microscope, and thus have very little effect on the visual pleasure the diamond induces.

Diamond carat

As stated, the diamond carat refers to the weight, not the size, of a diamond and has the biggest effect on a diamond's price. The higher the carat, the larger the original rough crystal - notoriously difficult to source, hence the effect on the price point.

CTTW looks at the total, combined weight of all of the diamonds in a piece of jewellery, and again, because of this, has a significant effect of price point.


Three key things to remember when assessing diamonds for purchase are to 'buy shy' (look for a weight that is below a full or half carat mark to save money), splurge on a decent cut over all else, and look for fancier shapes if you want to pay less (such shapes cost less per carat yet can appear larger).

You could also look for expert opinion to help review the quality of a piece, whilst insisting on a diamond grading certificate by an unbiased, independent body such as AGS or GIA, to verify the quality.

If you aren't sure whether a diamond is worth what it's being marketed, research different setting and look for similar diamonds to identify their price points in comparison.

Finally, once bought, have your piece appraised and insured - a grading report is essential for this - to ensure your money hasn't been wasted.

Diamond hunting might seem daunting, but once armed with the above information, you can shop like an expert appraiser and find yourself a real gem…

Check out our current jewellery auctions to see the beautiful pieces you could be making your own - we promise it'll be worth it!