The 4cs: Cut, Colour, Clarity, and Carat

A diamond’s charm is immediate. Influenced by proportion, light and balance, its presence is often recognised instinctively, before it is ever named. Moreover, every diamond carries its own quiet variations. Subtle shifts in form and light influence how it appears – and how it feels – once worn. To describe these qualities with clarity and consistency, gemological institutions such as GIA and IGI use a shared framework: the Four Cs. Cut, colour, clarity and carat give structure to these nuances. Together, they offer context beyond first impression – a language for understanding what the eye responds to, and why.

Diamond colour refers to the presence – or absence – of visible hue within the stone. The more colourless a diamond appears, the more freely light can travel through it, resulting in increased brightness and fire. Natural colour variation occurs during a diamond’s formation, influenced by trace elements in its environment. In mined stones, this can result in faint yellow or brown tones. In lab grown diamonds, the controlled conditions significantly reduce these variables, allowing for a higher proportion of colourless stones. While the full colour scale runs from D (colourless) to Z (light colour), lab grown diamonds are typically found within the near-colourless to colourless range. At Cullen, we prioritise stones that present a clean, luminous appearance – where colour never distracts from light.

Cut is the factor most closely tied to brilliance. It refers not to shape, but to how well a diamond’s facets are proportioned, aligned and polished. A well-cut diamond reflects light back through the crown with balance and precision. When proportions fall out of harmony – too shallow or too deep – light escapes through the lower facets, softening its sparkle. Because cut governs how a diamond performs in everyday light, it remains our most closely considered characteristic. At Cullen, we work exclusively with Excellent to Ideal cut stones, chosen for their clarity of reflection and refined presence.

Clarity refers to the internal and surface characteristics formed as a diamond grows. Known as inclusions, these features are typically microscopic – sometimes appearing as tiny black specks – and are most often only visible under magnification. Fewer inclusions generally increase rarity and value, but clarity is best considered in context. Many stones graded within the VVS to VS range appear entirely clean to the naked eye, offering purity without unnecessary excess. At Cullen, we select diamonds that balance clarity with integrity – stones that feel effortless in wear, without compromising on quality.

Carat measures a diamond’s weight, not its visible size. How that weight is distributed depends on shape and cut, meaning two diamonds of equal carat can appear very different in scale. Elongated silhouettes, such as pear or marquise cuts, often present with greater surface area, while deeper cuts may carry weight beneath the surface. For this reason, we consider millimetre measurements alongside carat to ensure proportion and presence feel aligned.

When assessing a diamond’s value, the 4Cs provide a point of reference. With natural variation from stone to stone, they offer a clear, objective way to understand differences that may not be immediately visible. That said, the Four Cs are not buying rules. They exist to support your decision, not dictate it.The final choice remains deeply personal – guided by instinct, and by the quiet connection you feel when something simply feels right.