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Tarratt has joined the Pragnell family Jewellery company

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A diamond embodies a moment, and the feeling it evokes for the wearer will forever be symbolic of that particular momentous occasion.

At Pragnell, our passion for jewellery – and all it represents – drives our commitment to creating an individual experience for every customer. This is what sets us apart. When it comes to diamond grading, we pay equal attention to each of the 4Cs: carat, colour, clarity and cut. Individually, they are all important, but when combined, they distinguish good diamonds from the very finest gems.


In terms of the 4Cs of diamond grading, the first to spring to mind for most people is the carat. The name derives from the carob seed, which was used by early gem traders as counterweights in their balance scales. Today, the size of a diamond is measured in carat weight, with 0.2g equalling one carat. This is divided into 100 points, so a diamond of 75 points weighs 0.75 of a carat. Although carat weight is the most obvious factor when determining a diamond’s value, two diamonds of equal size can in fact have disparate values, due to differences in their colour, cut or clarity.


As the world’s respected and foremost diamond grading laboratory, the GIA’s colour grading scale for diamonds is followed as the industry standard. Beginning with the letter D – representing completely colourless – the scale graduates in colour right through to Z. Even though each letter grade has a clearly defined range of colour appearance, the colour distinctions are so subtle that they are invisible to the untrained eye. However, these slight variations make a significant difference both in diamond quality and performance. The minimum colour requirement in our Diamond Collection for GIA certified diamonds is H.


Every diamond is unique. Another of the 4Cs is diamond clarity, which refers to the absence of inclusions or blemishes. It is rare for diamonds not to have any of these ‘birthmarks’, so it is this rarity that determines a diamond's value. Using the GIA International Diamond Grading System™, diamonds are assigned a clarity grade ranging from FL (flawless) to I3 (obvious inclusions) – with inclusions becoming visible to the naked eye at SI2. The minimum requirement in our Diamond Collection for GIA certified diamonds is SI1 (slightly included).


A well-cut diamond will reflect light internally from one mirror-like facet to another and back through the top of the gem. When arranged in precise proportions, the facets maximise reflection, refraction and vitality. Diamonds that are cut too deep or too shallow lose light, resulting in less brilliance and a less valuable stone. When classifying cut quality, a diamond's ‘finish’ is also taken into consideration. This includes polish (the overall condition of the facet surfaces) and symmetry (the precision and balance of a finished gem's cut). The minimum requirement in our Diamond Collection for GIA certified diamonds is "Very Good".


An understanding of diamond cut begins with the shape of a diamond. Largely a matter of personal preference, diamond shapes can vary from a marquise or a pear to an oval or a heart. Diamond cutting is a highly skilled craft and all cut shapes have specific guidelines to ensure they are considered ‘well cut’. The angle and placement of the facets used to create these distinctive cuts is very precise. Any deviation from the ideal proportions will affect the value of the finished gem.