When a diamond is tested for its quality in a showroom or workshop, it can be tested against others for several measurable properties. 

Dispersion: Dispersion refers to how much a stone can separate white light into spectral colours. A diamond’s dispersion is 0.044 and is considered high among gemstones. This is why a diamond has the ability to throw fire when it catches the light, delivering coloured flashes that sparkle alongside a white brilliance. Understandably, the way a diamond is cut affects its ability to disperse light.

Strength/Hardness: A diamond will resist scratching better than any other gemstone. It ranks at the top of the Mohs scale, making it ideal for rings and other everyday jewellery items. However, diamond’s hardness is measured differently from its toughness. A diamond can chip or leave crystallographic planes if struck hard and at the wrong angle, which highlights the importance of finding the right setting before finalising your perfect diamond jewellery design. 

Lustre/Brilliance: A stone’s lustre relates to its ability to reflect light from its surface. In doing so, a diamond can create brilliance, which refers to light specifically reflected from a stone’s facets. Together, a diamond’s brilliance and lustre combine to create a distinct, inseparable optical phenomenon. Diamonds have a high refractive index, resulting in intense reflections. Of course, skilful cutting will maximise a diamond’s return of light, as opposed to its brilliance being lost through the bottom of the stone. 

Pressure Resistance: Diamonds have a remarkable crystal structure that forms as a result of being compressed under the Earth’s pressure and high temperatures. But the pressure resistance of a diamond in its wearable form is understood by its ability to withstand everyday forces. Diamonds are durable but still vulnerable to chipping when struck with a sharp or dense object. Therefore, the proper and correct mounting of a diamond into its setting is paramount, as are periodic professional checks to guard against further potential damage. 

The industry standard for evaluating diamonds is the “4 C’s”. This terminology relates to the cut, clarity, carat weight and colour of a diamond. Each factor affects the price and appearance of the stone, and when considered together, can help you choose an optimal balance of all four to suit your budget and tastes. 

These four categories were established by the Gemological Institute of America and remain the global standard for examining the quality and features of a diamond today. 

Cut: The single most important visual factor of a diamond is the cut, which describes the proportions, symmetry and finish of the stone. If a diamond is cut to a high standard, it will return maximum light and will appear more fiery and brilliant than a stone that is cut poorly, even if its carat weight is higher. Excellent cut grades will guarantee the best visual performance.  

Colour: Every diamond is graded on a scale of D to Z. A stone graded as D refers to a colourless stone, the rarest of which sit within the D to F category, commanding high premiums. Diamonds categorised between G and J represent those designs that sit within the value-for-money sector and are ideal for warmer precious metal settings, since the colour of metal in a piece of diamond jewellery can often visually influence the stone’s perceived colour.  

Clarity: The clarity of a diamond refers to its internal and external blemishes or inclusions. A stone will be graded from flawless (FL) to I1-I3 (indicating inclusions). Most often, the inclusions within a diamond cannot be detected by the untrained eye and are microscopic. A diamond’s clarity grading should always be combined with its cut and colour for the best possible value.  

Carat: The carat rating of a diamond refers to its weight. The cut of a diamond can often affect its carat weight, meaning that two stones can sit side by side and appear completely different in size, yet weigh the same. Stone cutters usually prefer to prioritise the cut and visual size of a diamond rather than focusing on stones with higher carat figures, to avoid compromising on brilliance.  

There are many diamond shapes to explore when designing diamond jewellery. Each shape has its own character and appearance. To make this guide simple to digest, it’s easier to focus on five of the most common diamond shapes: round, princess, cushion, emerald and oval.  

Round Brilliant: The round brilliant-cut diamond is the most classic of all diamond cuts. Its shape is designed to maximise brilliance and fire, and for this reason, it remains the most common type of diamond cut you will see in modern jewellery designs. It’s also one of the most expensive diamond cuts per carat because of its rough-to-polished yield.  

Princess: The princess-cut diamond is a timeless square shape with a brilliant face arrangement, making it a modern and lively cut to feature in contemporary diamond jewellery designs.  

Cushion: Perfect for use in vintage-inspired jewellery designs, the cushion-cut diamond boasts a timeless appeal with a warm, romantic sparkle that makes it particularly well-suited for Art Deco designs. This diamond shape yields higher brilliance and fire, benefiting from comfortable round edges that make it incredibly practical if featured in a piece of daily wear jewellery.  

Emerald: The step-cut rectangular diamond, prized for its understated elegance and its clarity, is ideal for showcasing broad flashes of fire. Such an advantage also accompanies higher clarity, as its elongated shape creates the illusion of a larger stone, thanks to a unique “hall of mirrors” effect. In particular, the step cut showcases a greater internal purity than other cuts, making it a popular option for those who prefer their jewellery designs with an extra touch of panache and scintillation. 

Oval: The oval or pear-shaped diamond has the ability to elongate the finger when incorporated into a ring design. For that reason, it’s a particularly flattering diamond cut thanks to its teardrop effect. Pear diamond jewellery designs are also a slightly more affordable option than round brilliant-cut diamond jewellery designs, mainly due to their lighter carat weight.

Every unique design deserves the perfect setting to showcase its character. Here are four of the most common diamond settings used in jewellery design. 

Prong/Claw: The claw setting is excellent for brilliance. Not only is it one of the most popular diamond settings you’ll see in necklaces, earrings and rings, but it also allows for maximum light to pass through the meticulously arranged facets of a diamond. Four or six prongs are most common; the latter offers more security for the stone. 

Bezel: A bezel setting comprises a metal rim that surrounds the diamond’s girdle. Those with active lifestyles or a preference for modern designs will appreciate the simplicity and security of a bezel setting, which protects the base and sides of a diamond from damage. A bezel setting can sometimes reduce a stone’s perceived size, but certainly adds a bold silhouette to any diamond jewellery design. 

Halo: A halo setting features a circle of smaller diamonds surrounding a larger central stone. The arrangement is a popular one for increasing the central stone’s perceived size and sparkle. Often used to create the illusion of a much larger central stone, a halo setting is one way an artisan can achieve maximum impact without vastly increasing the centre carat weight of a design. 

For your first diamond purchase, nothing compares to sitting down with an expert from an established, award-winning independent jeweller like Banks Lyon. Our Lancaster and Kendal showrooms offer an extensive selection of ethical diamond jewellery designs. But if you need a little inspiration, you can enjoy a more tailored one-to-one experience with a member of our team of diamond experts.

Here, one of our designers will guide you through each step of our bespoke service, from your initial consultation over a glass of bubbles to the first pencil sketches and CAD designs and finally, your very own custom-designed masterpiece.