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Demystifying Diamond Quality: What's It All About?

At Fusion, we're lucky enought to have not one but two qualified gemmologists. Their qualification is called FGA (Fellow of the Gemmological Association of Great Britain) and it's crucial for being able to determine diamond quality with authority. One of these gemmologists is, in fact, so knowledgeable that they teach other jewellers who are studying for their FGA qualification and are regularly called up to give expert testimony in court.


Full disclosure: Neither of these two people is me! My "diamond grading" goes something like this:


"not very sparkly",

"quite sparkly"

"very sparkly" and

"wow!"


Not very helpful, I know, so here's the low-down on diamond quality and if it all seems too much to take in rest assured that our qualified and well-trained staff are on hand to help.


Understanding the Four C's of Diamond Quality


When purchasing a diamond, whether for an engagement ring, a special gift, or a personal indulgence, understanding how diamond quality is evaluated is essential. The quality of a diamond is determined by four key factors, often referred to as the Four C's: Cut, Colour, Clarity, and Carat weight. These factors help to assess a diamond’s overall value and appearance, and knowing how each one contributes to a diamond’s characteristics can make the buying process much clearer.


1. Cut: The Art of Shaping a Diamond


The "cut" of a diamond is perhaps the most important of the Four C's when it comes to its overall beauty. Unlike the other C's, cut refers to how well a diamond has been shaped and faceted by the jeweller, and it directly affects how well the diamond reflects light. A well-cut diamond will sparkle and shine, whereas a poorly cut diamond may appear dull, regardless of its other qualities.


Cut is graded based on several factors:


  • Proportions: The angles and symmetry of the facets.

  • Polish: The smoothness of the diamond's surface.

  • Symmetry: How aligned and uniform the facets are.



Gold ring with an emerald-cut diamond on a beige velvet cushion. Background includes soft-focus details with hints of blue and cream.
An emerald cut diamond solitaire ring on yellow gold band

Diamonds are usually graded for cut on a scale ranging from "Excellent" to "Poor." The more precise the cut, the more light is reflected, and the better the diamond’s brilliance. A diamond with an ideal cut can appear much larger and more dazzling than one with similar carat weight but a poor cut.


A teardrop-shaped diamond ring with halo setting on a reflective surface. The background shows blurred pink and beige tones.
Elegant tear-drop diamond ring featuring a stunning halo and diamond-set shoulders.
Diamond ring  setwith a starburst design of baguette cut diamonds around a brilliant cut diamond centre stone in a vintage box with dark velvet lining. Background features dried flowers and soft lighting.
A stunning starburst diamond ring featuring a cluster of baguette-cut diamonds radiating from a brilliant-cut centre stone.

2. Colour: The Subtle Spectrum of Diamonds


Although diamonds may seem colourless at first glance, they actually come in a wide range of shades. The second "C", Colour, refers to the presence of any colour within the diamond, with the highest quality diamonds being the most colourless.

The Gemological Institute of America (GIA) grades diamond colour on a scale from D (colourless) to Z (light yellow or brown). Colourless diamonds, graded D-F, allow the most light to pass through, enhancing their brilliance. Diamonds in the G-J range show faint to light yellow or brown hues, while diamonds in the K-Z range display more noticeable colour.

A colourless diamond is rarer and therefore more expensive. However, for some, a diamond with a slight tint may still offer great beauty at a more affordable price. The key is to find the right balance between colour grade and budget, while also considering the setting in which the diamond will be placed, as some colours may appear less pronounced against certain metals or backgrounds.


A marquise-cut yellow diamond ring with a halo of small diamonds in a white velvet box with a soft, blurred floral background.
A breathtaking marquise-cut yellow diamond ring, surrounded by a dazzling halo of smaller diamonds, gracefully displayed in its box.

3. Clarity: The Purity of a Diamond


The "clarity" of a diamond refers to the presence of any internal or external imperfections, known as inclusions and blemishes, respectively. Most diamonds have some degree of imperfection, although the best diamonds are those with few or no visible flaws.

Clarity is graded on a scale from Flawless (FL), which has no internal or external imperfections visible under 10x magnification, to Included (I1, I2, I3), where inclusions are noticeable to the naked eye and may affect the diamond’s durability and appearance.

Common inclusions include tiny minerals, cracks, or clouds that form naturally during the diamond’s creation under intense heat and pressure. While clarity is important, many inclusions are microscopic and do not affect the diamond’s brilliance. In fact, some inclusions can even give a diamond character and uniqueness. However, the clearer the diamond, the rarer—and often the more valuable—it is.


Heart-shaped diamond ring on platinum band conveying elegance and romance.
A magnificent heart-shaped diamond set on a refined platinum band, symbolizing elegance and romance.

4. Carat Weight: The Size of the Diamond


The final "C" is carat weight, which measures the size of the diamond. One carat equals 200 milligrams, but the size of a diamond is not solely determined by its weight. The dimensions of the diamond, including its cut and depth, also play a significant role in how large or small it appears.


While carat weight directly affects the price of a diamond, it’s important to remember that a larger diamond with lower quality in the other C's may not be as visually appealing or valuable as a smaller, higher-quality stone. A well-cut, smaller diamond can often appear larger and more dazzling than a poorly cut, larger one.


How the Four C’s Work Together


When evaluating a diamond, all four C's work together to determine its overall quality and appearance. For instance, a diamond with an excellent cut will look stunning even if it has a lower colour or clarity grade. Conversely, a diamond with high colour and clarity but a poor cut may appear lacklustre.


It’s also worth noting that personal preference plays a role in assessing the Four C’s. Some buyers prioritise a diamond’s size (carat weight), while others may place more importance on the diamond’s brilliance (cut) or clarity. Additionally, the setting in which the diamond will be placed can influence how certain qualities are perceived.

Marquise diamond ring with platinum band on a reflective surface. Blurred background with pink and blue flowers. Sparkling, elegant setting.
Marquise diamond ring with a platinum band, an elegant and timeless design.

Conclusion


The Four C’s provide a comprehensive and standardised way of assessing diamonds, but understanding how each factor contributes to a diamond’s appearance, rarity, and value can help you make an informed decision. Whether you are purchasing a diamond for its beauty, investment potential, or sentimental value, knowledge of the Four C’s will enable you to select a stone that meets your needs and preferences.

By carefully considering each of these characteristics—cut, colour, clarity, and carat weight—you can ensure that your diamond purchase is a choice you’ll be happy with for years to come.


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