A Guide to Buying Diamonds: The Four Cs Explained

Diamond engagement rings are still the most popular choice for engagment rings for couples by far, and they have been ever since De Beers launched its famous “A Diamond is Forever” campaign in 1947. And while we love anything that sparkles here at One Fab Day, if you’re thinking of investing in diamonds either a your ring or another piece of jewellery, it’s worth knowing that not all are created equally. In fact there’s a whole grading system which dictates the quality, rarity and therefore the value of the gem you’re about to purchase. This is known as the four Cs, and relates to the four qualities you should consider when diamond hunting – Cut, Colour, Clarity and Carat! And yes, that is in order of importance. But what are the four Cs and how important is each one? Here, we’ve broken each of the four Cs down as a handy guide to read before you hit the jewellers. This will help you to know what to expect within your budget, whether you’re buying new or going vintage. Let’s dive in…

The Four Cs of Diamonds

Photo by Natasha Sherling


The most important category when it comes to the four Cs of diamonds is the cut. You might ask yourself: Why is the cut of a diamond top of the list? Essentially, it’s because the cut of the diamond is responsible for the main magic that comes with a diamond – its sparkle. The better the cut – its angles and facets – the more your ring will reflect and refract beams of light, thus giving you maximum brilliance and ‘fire’. However, a poorly cut diamond will look dull even if it scores well in the areas of colour and clarity. The GIA diamond cut chart grades diamond cut on the scale of Ideal, Excellent, Very Good, Good, Fair and Poor, so say if a diamond cutter cuts a stone so that it’s deeper, for instance to maintain its weight or carat, that won’t reflect the light in the best way, and therefore the cut is considered poor.

Diamonds The Four Cs

Photo by Wonder & Magic via One Fab Day


The second most important element to consider when it comes to diamond shopping is the stone’s colour. There is a very specific colour grade used to determine the quality of a diamond, with white or colourless gems being the rarest and priciest option, and yellow being the poorest quality option. Naturally, there’s a huge scale between the best and worst diamond colours, but it can be tricky to tell the difference from ring to ring without checking and comparing options against one another.

Diamonds The Four Cs

Photo by Rosie & Dott


Clarity is a critical aspect to inspect when you’re buying a diamond and relates to how ‘clean’ a stone is. It comes down to examining the ring’s markings, flaws, and imperfections, also known as inclusions. The more flawless the ring, the more rare and expensive that ring will be.

Diamonds The Four Cs

Photo by Aoife O Mahony Design


The final feature of the four Cs is carat, which is the measure of the mass or weight of the diamond. It’s not simply a matter of ‘bigger is better’ to the naked eye – that’s a common misconception when it comes to diamonds. Rather, it’s the weight of the diamond which is the key element when it comes to a reflection of its quality. Two diamonds of the same carat can actually look significantly different in size depending on their cut.

Check out our post on the top tips for buying an engagement ring here or browse Ireland’s best jewellers. Alternatively, take our quiz to discover what kind of ring is perfect for you.