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Diamond Cut

A diamond's cut refers to its shape, alignment and proportions. Each shape is formed from a number of facets, whose angles and proportion determine how light refracts through the stone. The cut of a diamond can be seen on each stone’s GIA certification, it acts as a visual representation of a diamond's proportions and their impact on its light performance. It illustrates how a diamond's cut influences its brilliance, fire and ultimately its sparkle.

The cut of a diamond also refers to its physical shape, this the outline of the diamond and is often one of the biggest considerations when choosing your diamond and how your finished design will look. There are many different diamond shapes, from round brilliant to cushion, from oval to radiant, each offers something completely unique.

Diamond Colour

A diamond is a rare natural material which can form in a wide range of colours, from vivid pink to intense blue, from pure white or colourless to fancy vivid yellow.

The Gemmological Institute of America (GIA) grades a diamond’s colour on a scale from D to Z, with D representing pure white, colourless stones. These colourless stones are considered the rarest and most valuable, offering the wearer brightest diamond possible.
The difference between two colour grades can make a significant difference to the price, but may not always be visible to the naked eye. It is always important to consider which of these factors, cut, colour, clarity and carat are the most important to you, to ensure we can source and select the very best stone for your budget.

Diamond Clarity

As with any natural material, each diamond contains unique characteristics. These are known as inclusions or imperfections. The clarity of a diamond is determined by how many of these inclusions a particular stone has, and how large, obtrusive or obvious they are.

The scale starts at F/IF (Flawless/Internally Flawless), through to I1 or I2. The diamonds at the upper end of the scale will not have any visible inclusions, while an I1 or I2 diamond may have large flaws which are visible to the naked eye.

Each diamond in our collection is a minimum of an SI1 meaning that inclusions are only noticeable to a skilled grader under 10x magnification.

Diamond Carat

A carat is a technical unit of measurement used to describe a diamond’s weight. One carat is divided into 100 points, so that 0.75cts would translate to 75 points. The carat weight often determines how large a diamond will appear, although this can be affected by the cut. For example, an oval, emerald or pear cut diamond will often appear larger than a round brilliant cut diamond of the exact same weight.

It is also important to note that certain carat weights – such as half, one or two carats – are often in greater demand, so their price can be higher than slightly lighter or slightly heavier carat weight stones.


A diamond’s certification describes its unique characteristics and establishes its authenticity, providing complete peace of mind. Many of the diamonds Prestons showcases are independently certified by the Gemological Institute of America (GIA). The GIA is internationally renowned as a reputable and reliable organisation. Each certified diamond will be accompanied by physical or digital papers detailing its features, confirming its authenticity and quality.

While a diamond’s colour, cut, clarity and carat help to determine its value, there is no substitute for human expertise in deciding the quality of a stone’s unique personality.

In selecting our diamonds and gemstones, our buyer only chooses those whose beauty exceeds their on-paper certification. Our showroom teams will always have an open and honest conversation with any client about their specific requirements and preferences, in order to find the perfect stone for them.

Our Commitment To Ethical Diamonds

Here at Prestons, we use the finest diamonds and gemstones to create our in-house collections and bespoke commissions. The team at our London workshop understands the responsibility that comes with such rare natural materials and are committed to sourcing the highest quality diamonds and gemstones only from the most reputable, ethical and conflict-free sources.

Discover Prestons

Our showrooms in Wilmslow, Guildford, Norwich and Leeds are always here to help and continue to offer the advice and guidance that has been our hallmark since 1869.

Our Showrooms

Over the years, generations of families have become customers of Prestons, and many have gone on to become friends. Today, our teams look forward to welcoming you to our showrooms in Wilmslow, Guildford, Norwich and Leeds.

Prestons Guildford


Our Guildford showroom, which is now located on the opposite side of the high street, is designed to reflect the architectural merit of the Edwardian building it now occupies. The store features newly extended spaces dedicated to the fine watch houses it showcases, alongside a comfortable lounge to allow our clients to explore our bridal and fine jewellery collections. Explore This Showroom

Prestons Wilmslow


Located in the heart of Wilmslow, this showroom features a selection of spaces dedicated to the fine watch houses it showcases. Of course, the bridal collections Prestons have always been famous for remain a prominent feature of the store and surround the famous Aquarium Bar which sits at its centre. Explore This Showroom

Rolex by Prestons, Leeds


This showroom, located in Victoria Gate, features extensive Rolex showcases alongside a discrete VIP lounge. Every element of the interior design radiates the values of the Rolex crown: excellence, precision and attention to detail from louvre walls in walnut, to the careful calibration of colours and patterns within the fittings and furnishings. Explore This Showroom

Prestons Norwich


Located on the historic Norwich high street, Prestons Norwich has been expanded and redesigned to reflect the character of the building it has occupied for over 150 years. The showroom features collections by Patek Philippe, Rolex and TUDOR alongside our fine jewellery collections. Explore This Showroom
Guildford showroom