Understanding the qualities that shape a diamond’s beauty and value can make the selection process far clearer. This guide outlines the key characteristics used to assess diamond quality and how they influence both appearance and price.
What is a diamond?
Diamonds are the hardest natural mineral on earth, formed deep beneath the planet’s surface billions of years ago. Under immense heat and pressure, carbon atoms bond together to create these remarkable crystals. Their exceptional hardness and ability to reflect light are what give diamonds their brilliance and enduring appeal.
NATURAL VS LAB GROWN
NATURAL DIAMONDS
Natural diamonds formed deep within the Earth over billions of years before being brought closer to the surface through ancient volcanic activity. Their geological origin and natural scarcity are part of what has made them so prized throughout history.
LAB GROWN DIAMONDS
Lab-grown diamonds are created in specialised facilities using technology that replicates the high-pressure conditions under which diamonds naturally form. They share the same chemical composition and physical properties as natural diamonds.
While the two appear virtually identical, their origins - and the way they behave in terms of rarity and long-term value - are quite different.
The 4Cs
CUT
The cut of a diamond refers to its facets, symmetry and proportions, which greatly influence its sparkle. While shape describes the outline of the diamond when viewed from above, the cut determines how effectively the stone reflects light. Round brilliant diamonds follow a precise formula of angles and proportions. Elongated shapes such as ovals or pears allow the cutter more flexibility, which can sometimes affect the final result. Poorly cut elongated diamonds may display what is known as the bowtie effect, where light leakage creates a dark bow-tie shaped shadow across the centre of the stone.
CARAT
Carat refers to the weight of a diamond and is often associated with its size. Generally, a higher carat weight leads to a higher price, although the other quality factors also play an important role. Diamonds that fall exactly on whole carat weights, such as 1.00 carat - tend to carry a significant price premium. Stones just below these thresholds, such as 0.96 carats, may appear nearly identical in size while offering better value.
COLOUR
White diamonds are graded on a colour scale developed by the Gemological Institute of America (GIA), ranging from D to Z. Diamonds graded D-F are considered colourless and are the rarest. As the scale progresses, subtle warmth becomes more visible. For most engagement rings, I generally recommend diamonds within the H range or higher, where the stone still appears bright and white once set. Champagne diamonds are graded using a separate scale ranging from C1 to C8.
CLARITY
Clarity refers to the presence of internal characteristics known as inclusions. These are graded under 10× magnification using a scale developed by the GIA. I typically focus on diamonds within the VVS1 to SI2 range, depending on the client’s priorities and budget. Well-selected SI1 and SI2 stones can often offer an excellent balance between appearance and value, which we can explore during the stone selection process.
CERTIFICATE
I consider the certificate the 'fifth C.' Independent laboratories assess diamonds and provide an objective evaluation of their quality. The Gemological Institute of America (GIA) is widely regarded as the most consistent and respected grading authority. Some grading organisations apply more lenient standards, which means a diamond labelled as a higher colour or clarity grade may not meet the same standard under GIA assessment. For natural white diamonds, I primarily source GIA-certified stones, while IGI is the most common grading laboratory for lab-grown diamonds. Champagne diamonds typically do not receive certification, which contributes to their more accessible pricing.
Choosing a diamond is a considered process. During a bespoke enquiry, I guide you through each option to help you select a stone that feels right - both visually and practically.