Diamond Guide

Our guide to the 4 Cs

"Show me the rock!" is the first thing you hear after getting engaged. But before you buy up big, read our guide to the 4 Cs — so you end up with your dream ring

Carat

This is the weight of your diamond. One carat equals 0.2 grams. Carat is also subdivided into 100 points, which is why you'll find diamonds that are 0.75 points (three quarters of a carat), or 0.25 points (one quarter of a carat). The most important thing to remember with carat is that bigger is not necessarily better. Obviously the size of the diamond is a huge contributing factor to its value, but you could have two diamonds of equal size and have very unequal value due to different qualities. This is where the cut, clarity and colour come in.

Clarity

Almost all diamonds contain small marks called inclusions. They can appear as cracks, dark sports or tiny chips, which can only be seen through magnification. However, these blemishes can interfere with the passage of light through the diamond. Make sure you ask your jeweller how the specific inclusions in your diamond affect its sparkle. A diamond's clarity is also graded, with flawless diamonds having no flaws whatsoever. For your engagement ring, a diamond graded between VVS1 and S12 is of excellent quality, with the flaws unnoticeable and the sparkle unaffected.

Colour

Most diamonds have some hint or trace of colour, mainly yellow. The closer a diamond is to not having a colour, the more rare and valuable it is: diamonds without any trace of colour are extremely rare. Any tint of colour in a diamond restricts light reflection and dulls the sparkle. Your jeweller will be able to tell you the colour grading of your diamond. The colour is classed on a scale from D to Z, with D-grade being colourless (and very expensive) and Z-grade being light yellow. The tint in diamonds graded "H", "I" and "J" is mostly invisible to the naked eye, and they are all suitable quality diamonds for engagement rings. Anything of a lower grade than this would be visibly yellow.

Cut

The quality of the cut determines the value of the diamond — and that amazing sparkle factor. A well-crafted diamond — that is, a diamond cut to precise angles — will reflect light from one facet to another then out through the top of the diamond. Most diamonds have 58 symmetrical facets. The proportions of your diamond also affect the quality: if they're cut too shallow or deep, the light won't be able to bounce around properly and the diamond will look duller.