Diamond Buying Guide: The 4Cs Explained

Cut refers to how well a diamond's facets are proportioned and angled, not its shape (round, princess, oval, etc.). A well-cut diamond reflects light beautifully and appears brighter; a poorly cut one can look dull even if it's a good size. Of the 4Cs, cut has the biggest visible impact on how lively a diamond looks.

Diamond colour is graded on a scale from D (completely colourless, the rarest and most valuable) down through the alphabet as a faint yellow or brown tint becomes more visible. Most jewellery-grade diamonds fall in a range where the colour difference is barely noticeable to the untrained eye, especially once set in gold or white metal.

Almost all natural diamonds have tiny internal marks called inclusions, formed naturally as the diamond grew. Clarity grades range from "Flawless" down to grades where inclusions are visible to the naked eye. For most jewellery, a clarity grade where inclusions are only visible under 10x magnification offers excellent value — you don't need to pay for a level of clarity you'll never actually see.

A carat is a unit of weight (0.2 grams), not a measure of visual size directly — cut quality affects how big a diamond of a given carat weight appears. Price doesn't rise in a straight line with carat weight either; diamonds just above round-number weights (like 1 carat) are often priced at a premium compared to ones just below.

A certificate from an independent gemological laboratory records a diamond's 4C grading, so you're not relying on the seller's word alone. For any diamond above a modest size, it's reasonable to ask whether it comes with independent certification, and to have the certificate details match the stone you're buying.