Buying Diamonds: Navigating the 4 Cs of the diamond world

There was once a time when buying diamonds meant embarking into a time-consuming and often confusing journey through incongruent metrics and sizing charts. The process became infinitely easier when the Gemology Institute of America (GIA) universalised international gemstone measurements. Now, becoming an amateur diamond expert is only as difficult as familiarising yourself with the 4 Cs – clarity, cut, colour and carat weight.

Stone cutting is one of the qualities to look at when buying diamonds

Carat Weight

The old adage ‘bigger is better’ definitely holds true when it comes to gemstones, and carat weight is perhaps the most basic measurement to look at when it comes to buying diamonds. Prices increase exponentially as carat weight increases. Why? Because larger stones are rarer, more desirable and infinitely more challenging to design. While it’s tempting to go for the largest rock you can afford, always remember to balance it with cut, colour and clarity. 


Did you know that naturally-occurring diamonds are formed when carbon in the planet’s crust is exposed to extreme heat and pressure? It probably comes as no surprise, then, that minerals in close proximity also get added to the process. These additional blemishes, known as inclusions in the gemology world, significantly reduce overall appearance. So if you’re aiming for a top-quality stone, opt for ‘flawless’ or ‘internally flawless’ clarity.

When buying diamonds, pay attention to clarity


Although one might assume that cut refers to the shape of the diamond (round, oval, square, etc), it is, in fact, a grading that reflects how well a gemstone’s facets reflect light. Of all the 4 Cs, this is the only one influenced by man rather than Mother Nature. A professional cutter shapes the rough diamond for the best possible symmetry and shine. Any cuts that are too shallow or deep will create a dull, lacklustre finish, while a well-cut stone can appear larger than its true size!  


When it comes to buying diamonds, the term ‘colour’ is something of a misnomer, as they are actually prized for the lack thereof. At the top of the charts are completely colourless D-grade stones, while at the other end of the spectrum, Z-grade gems have a distinctly yellow tinge. If you’re really looking for a dazzling showstopper, D diamonds are the way to go.

Diamonds range from D to Z grades

While each of the 4 Cs directly influences any diamond, it is the combined interplay between them that creates the ultimate look and appeal. Talk to a reputable jeweller about your budget and gem requirements for the best results. When buying larger stones, always make sure to ask for the accompanying GIA certificate to ensure authenticity.

If you’re interested in learning more about diamond grading, GIA offers some exclusive courses in Hong Kong. Find out more details on their website here

Text: Tenzing Thondup