Understanding Diamonds

The 4 C’s
Clarity, Cut, Colour and Carat

Our Understanding Diamonds page is a useful guide designed to help you learn about diamonds. It explains the four Cs—Clarity, Cut, Colour, and Carat—making it easier to make informed decisions when purchasing diamonds. Whether you’re a first-time buyer or a diamond enthusiast, this page provides valuable insights to ensure you understand the key aspects determining a diamond’s quality and value.


Clarity refers to the presence and visibility of imperfections, or ‘inclusions,’ within a diamond. These inclusions can be tiny fractures or minerals embedded within the stone. When examined with a loupe, a 10x magnifying tool used by jewellers, these inclusions may resemble minute clouds, crystals, or feathers. The size and location of these inclusions are significant in determining the diamond’s value. Inclusions located on the side can often be concealed by the setting and may not greatly affect the stone’s beauty or brilliance. However, inclusions positioned at the top or centre of the diamond can interfere with light dispersion, reducing the diamond’s brilliance and desirability.

    Diamond Clarity Descriptions

    Clarity is assessed on a scale ranging from Flawless (FL) to Included (I), with the following grades:

    • FL Flawless: No inclusions or surface blemishes visible under 10x magnification.
    • IF Internally Flawless: No inclusions and only insignificant surface blemishes visible under 10x magnification.
    • VVS1 – VVS2 Very, Very Slightly Included: Extremely difficult to see inclusions. Difficult to see inclusions
    • VS1 – VS2 Very, Slightly Included: Difficult to see inclusions
    • SI1 – SI2 Slightly Included: Inclusions are more noticeable.
    • I1 – I3 Included: Inclusions visible to the naked eye, sometimes referred to as P1 – P3 or ‘piqué.’


    Cut refers to the angles and proportions of a diamond, as well as the craftsmanship involved in transforming the original rough diamond into a faceted gem that maximises its fire and sparkle. Diamond cutting is an art that relies on scientific principles to ensure that light is reflected optimally from one facet of the diamond to another. If a diamond is cut too deeply or too shallowly, it will ‘leak’ light from the sides and bottom rather than directing it through the top, resulting in reduced brilliance.

    Cut is often regarded as the most crucial of the 4Cs, but assessing the quality of a diamond’s cut is less developed than grading its clarity and colour. While new software and techniques are emerging to establish more precise standards for cut quality, they are not yet widely adopted.

    Cut also pertains to the shape of the diamond. The round diamond, also known as a brilliant cut, is the most common because its shape optimises light reflection. Other shapes include square, pear, marquise, princess, trillion, and heart. Our gemmologists can explain the criteria for an excellent cut in each of these shapes.

    Diamond Cut Descriptions

    Round Brilliant Diamonds

    This shape sets the benchmark for all other diamond shapes, representing over 75% of diamonds sold today. Its 58-facet cut, distributed among the crown (top), girdle (widest part), and pavilion (base), is meticulously calibrated to maximise fire and brilliance.

    Oval Diamonds

    Featuring an even, perfectly symmetrical design, the oval shape is popular among women with small hands or short fingers. Its elongated form creates a flattering illusion of length for the hand.

    Marquise Diamonds

    This elongated shape with pointed ends was inspired by the charming smile of the Marquise de Pompadour and commissioned by France’s Louis XIV, the Sun King, who desired a diamond to match it. It is stunning as a solitaire or when complemented by smaller diamonds.

    Pear Shaped Diamonds

    A hybrid cut combining the best features of the oval and marquise shapes, the pear-shaped diamond resembles a sparkling teardrop. This design is particularly flattering for hands with small or average-length fingers and is especially beautiful in pendants or earrings.

    Heart Shaped Diamonds

    The ultimate symbol of romance, the heart-shaped diamond is essentially a pear-shaped diamond with a cleft at the top. The cutter’s skill determines the cut’s beauty, so look for a stone with an even shape and a well-defined outline.

    Emerald Cut Diamonds

    Characterised by a rectangular shape with cut corners, the emerald cut is known as a step cut due to its concentric broad, flat planes resembling stair steps. Since inclusions and inferior colour are more noticeable in this cut, it is essential to select a stone with superior clarity and colour.

    Princess Cut Diamonds

    A square or rectangular cut with numerous sparkling facets, the princess cut is relatively new and often features in solitaire engagement rings. It flatters hands with long fingers and is frequently adorned with triangular stones at the sides. To maximise brilliance, this cut directs more weight towards the diamond’s depth, with depth percentages of 70% to 78% being common.

    Trilliant Diamonds

    This spectacular wedge of intense fire was first developed in Amsterdam. The exact design can vary based on a diamond’s natural characteristics and the cutter’s preferences. It can be a traditional triangular shape with pointed corners or a more rounded triangular shape with 25 facets on the crown, 19 facets on the pavilion, and a polished girdle. It is ideal for the adventurous.

    Radiant Cut Diamonds

    Combining the elegance of the emerald shape with the brilliance of the round cut, the radiant cut features 70 facets to maximise colour refraction. To achieve maximum brilliance, this cut directs more weight towards the diamond’s depth, with depth percentages of 70% to 78% being common.

    Cushion Cut Diamonds

    An antique style, the cushion cut resembles a blend of an Old Mine Cut (a deep cut with large facets popular in the late 19th and early 20th centuries) and a modern oval cut.


    Colour refers to how ‘colourless’ a diamond is. The grading scale ranges from the highly sought-after, icy white perfection of D (colourless) to Z, which denotes diamonds with more noticeable brown or yellow hues. The differences in colour are extremely subtle. To ensure consistent comparisons, laboratories use a master set of stones and controlled lighting conditions that avoid ultraviolet light. These master stones define the boundaries of the colour scale, aiding diamond graders in determining the appropriate colour grade.

    Once you become familiar with what to look for, you will be able to discern the subtle variations in tone. The choice of colour grade is ultimately a matter of personal preference and budget. Not all diamonds are white; rare ‘fancy’ diamonds can be found in stunning shades of canary yellow, soft blue, green, orange, pink, and the exceptionally rare red. Black and brownish/beige diamonds, often referred to as ‘champagne’ diamonds, are also particularly fashionable at the moment.

    Carat Weight

    Carat refers to the weight of a diamond rather than its size, as is often mistakenly believed. One carat is equivalent to 200 milligrams or one-fifth of a gram. A carat can be subdivided into 100 ‘points’, meaning that a diamond weighing ¾ of a carat can also be described as having 75 points, being a 75-pointer, or weighing 0.75 ct. When considering diamonds with comparable clarity, colour, and cut gradings, their weight is the primary factor influencing their rarity. High-quality large diamonds are rare and, therefore, highly valued.

    Diamond Anatomy & Cut Quality

    The three key components of a diamond’s anatomy are its diameter, table, and depth. The ratios of the table to the diameter and the depth to the diameter are crucial in determining a diamond’s cut grade. While having knowledge of a diamond’s anatomy can be beneficial, the cut grade should primarily guide your diamond purchasing decisions.

    Here, we explain the various parts of a diamond to help you familiarise yourself with the terminology used to describe a diamond’s features.


    The width of the diamond is measured through the girdle from side to the other.


    The flat surface area at the top of the diamond, the table, is usually the largest facet of the stone.


    The upper part of a diamond, extending from the girdle to the table.


    The girdle sits between the crown and the pavilion and defines the perimeter of the diamond. The optimum size is a medium-thickness girdle. An extremely thin girdle can make the diamond more vulnerable to chipping. However, a thick girdle is also undesirable because it adds additional weight to the middle of the diamond, which can cause the diamond to look smaller than diamonds of similar weight.


    The pavilion is the bottom portion of the diamond, the section extending from the girdle down to the culet. A pavilion that is too deep or shallow can result in light escaping from the bottom or side of the stone. The desired performance of a diamond is to reflect the light out from the top of the stone.


    A tiny facet at the bottom end of the gemstone, often ending in a tip or point. The preferred culet is not visible to the unaided eye.


    The overall height of the diamond measured in millimetres, from the culet to the table of the diamond.

    Laboratory-Grown Diamonds

    At Coppins, our approach to laboratory-grown diamonds is both thoughtful, adaptable and considered. While these man-made diamonds do not feature in our own one-off pieces or pre-designed collections, we are open to incorporating them into bespoke pieces for our clients.

    As gemmologists we have a deep rooted passion for unique gemstones, each with its own enchanting history and chemical make-up. We celebrate the distinctive hues, shapes, and origins of these stones, appreciating their long journey from the depths of the earth.

    For our ready-to-wear jewellery, we exclusively use natural diamonds, valued for their rich, storied backgrounds. However, we recognize the merits of synthetic diamonds and are willing to use them in custom designs, appreciating their comparable qualities and properties while acknowledging their differing stories of creation.