Diamond 4Cs Guide

When choosing the perfect diamond, the process can feel slightly daunting with so many factors to consider. You may have come across the 4 Cs, which play a significant role in determining a diamond's price, quality, and aesthetics. Let's explore what each of these Cs entails and how they influence your diamond selection.


Diamond 4Cs Guide

When choosing the perfect diamond, the process can feel slightly daunting with so many factors to consider. You may have come across the 4 Cs, which play a significant role in determining a diamond's price, quality, and aesthetics. Let's explore what each of these Cs entails and how they influence your diamond selection.


Synthetic, laboratory grown, laboratory created, man-made, or cultured diamond: Lab grown diamond

Scintillation: This phenomenon refers to the dazzling play of light and flashes of brilliance that occur when a diamond is moved or observed from different angles. It is a visual effect caused by the interaction of light with the diamond's facets, creating a sparkling and dynamic appearance.

Inclusions: An inclusion is a cavity or crystal cluster within a gemstone. These can cause problems if they form too close to the surface, and their presence will often decide the value of a stone

IGI: International Gemological Institute

GIA: Gemological Institute of America

Brief History of the 4Cs

The concept of the 4Cs was pioneered by Robert M. Shipley, the founder of GIA, in the early 1900s to establish a definitive method for grading diamonds. Prior to the development of the 4Cs, diamond grading lacked uniformity, leading to variations in the perceived quality of diamonds based on subjective opinions.

Today, the 4Cs serve as the universally accepted standard for grading diamonds, providing a consistent and transparent framework for assessing diamond quality across the globe. This standardised approach ensures that consumers can make informed decisions when purchasing diamonds.

What are the 4Cs?

The 4Cs are characteristics used to determine the quality of a diamonds. This way of grading diamonds takes into account 4 factors:

1. Carat Weight

Carat weight is a measure of a diamond's size, with one carat equal to 200 milligrams. Larger diamonds generally have a higher carat weight and are considered more valuable.

2. Cut

The cut of a diamond refers to its proportions, symmetry, and polish. A well-cut diamond reflects light effectively, resulting in enhanced brilliance and sparkle.

3. Colour

Diamond colour is graded on a scale from D (colourless) to Z (light yellow or brown). The less colour a diamond exhibits, the higher its grade and value.

4. Clarity

Clarity assesses the presence of internal flaws (known as inclusions) and external blemishes in a diamond. Diamonds with fewer inclusions and blemishes receive higher clarity grades and are considered more valuable.

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Carat Weight

Let's explore how carat weight impacts both the quality and visual appeal of a diamond. The carat weight of a diamond significantly contributes to its perceived value and overall size.

1. What is Carat Weight?

Carat, abbreviated as 'ct', measures a diamond's weight. While two diamonds may share the same carat weight, variations in appearance arise from factors like cut and shape. A diamond's cut can influence its perceived size, potentially making a diamond appear larger despite having a lower carat weight than another.

2. Carat Weight and Price

The carat weight of a diamond directly influences its price, but this isn't the only factor that contributes to the overall price of a diamond. Its also important to note that natural diamonds and lab grown diamonds hold different values per carat, with lab grown diamonds being much cheaper than natural ones. Read our guide on lab grown diamonds to learn more about how you can make the most of your budget by choosing a lab grown diamond.

3. When Did We Start Measuring Diamonds in Carats?

The practice of measuring diamonds in carats has ancient roots. The term "carat" originates from the historical use of carob seeds, known for their consistent weight, as a unit of measurement for gemstones. While the concept of carat weight for diamonds evolved over time, it wasn't until the early 20th century that the metric carat, equivalent to 200 milligrams, became the standardised unit of measurement for diamonds and other precious gemstones. This standardisation ensured uniformity and accuracy in assessing diamond size and value within the jewellery industry.

4. What Effect Does Carat Weight Have on the Size of a Diamond?

The carat weight of a diamond directly impacts its size, so the larger the carat weight, the bigger the stone. However, specific cuts and shapes can affect the diamond's appearance, sometimes causing a gemstone with a lower carat weight to appear larger than its actual size.

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The cut of your diamond can drastically change the way it looks. Let's discover what kind of cut makes diamonds truly sparkle.

1. What is a Diamond Cut?

The cut refers to the proportions, symmetry, and overall craftsmanship of the diamond's facets, which directly influence its brilliance, fire, and sparkle.

2. What is the Best Diamond Cut?

GIA designates the top natural diamond cut as "Excellent," while IGI grades the finest lab diamond cut as "Ideal." These classifications signify diamonds crafted with utmost precision, boasting precise angles, symmetry, proportions, facet balance, and superior polish achieved by highly skilled diamond cutters. Such meticulous cutting results in diamonds that reflect light flawlessly, maximising the stone's brilliance, fire, and sparkle.

3. Why is Cut Important for a Diamond?

Considered the most crucial of the 4Cs, the cut of a diamond determines its brilliance, sparkle, and scintillation by influencing the proportions and symmetry of the stone when it's cut.

For instance, the round brilliant cut is frequently lauded for its exceptional sparkle due to its multitude of small facets, which create a mesmerising display of multicoloured light when illuminated.

4. Which Cut Has the Most Sparkle?

The round brilliant cut diamond is renowned for its unparalleled sparkle, attributed to its numerous lines of symmetry and 58 facets that optimise light reflection within the diamond. Consequently, their exceptional sparkle often places them among the pricier options among diamond cuts.

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Explore the spectrum of diamond hues to discover which colours elevate the elegance of your jewellery pieces.

1. What is Diamond Colour?

The GIA utilises a grading scale for diamond colours ranging from D (colourless) to Z (slightly coloured) to evaluate and categorise diamonds based on their hue. Diamonds with a D grade are considered the most valuable due to their exceptional lack of colour, while those closer to Z may exhibit subtle tints of yellow or brown. This grading system ensures transparency and consistency in assessing diamond colour quality across the industry.

2. Colour Scale for Diamonds

Following the GIA's colour grading system, diamonds with higher grades exhibit less colour, with completely colourless diamonds receiving the highest grades. Conversely, diamonds with poorer colour grades may display tints of yellow or brown and will consequently receive lower scores on the GIA's grading scale. Refer to the diagram below for a visual representation.

3. How is a Diamonds Colour Grade Determined

At Jessica Flinn, we collaborate exclusively with top-tier diamond suppliers, guaranteeing the highest standards of quality at all times. Each diamond we receive comes with an assigned colour grade, which we meticulously verify and include in its certificate.

4. Which Colour Diamond is Right for You?

When selecting a diamond colour, several factors come into play. Diamonds with higher color grades typically command higher prices compared to those with lower grades. For budget-conscious buyers, diamonds graded G and lower may be more suitable, although it's worth noting that grades below H may exhibit slight yellow or brown tints.

Alternatively, lab-grown diamonds offer the same sparkle as high-grade natural diamonds but at a lower price point. Their controlled laboratory environment makes it easier to produce diamonds with clearer appearances, meaning higher grade lab diamonds are in higher abundance than their natural counterparts.


Discover the diamond clarity grading scale, delve into the realm of diamond inclusions, and understand why a genuinely flawless diamond is exceptionally rare. 

1. What is Diamond Clarity?

Clarity refers to the presence of internal flaws (inclusions) and external blemishes in the diamond, which can affect its overall appearance and brilliance.

2. Clarity Scale for Diamonds

A diamonds clarity is measured on a scale from FL (flawless) to I3 (very heavily included). Within this scale, VS2 (very slightly included) to SI1 (slightly included) is acknowledged as the optimal range, offering both value and eye-clean beauty. Flawless diamonds, characterised by minimal inclusions, stand as the rarest and most prized among all.

3. How is a Diamonds Clarity Grade Determined?

As natural diamonds undergo formation in the Earth over billions of years, the intense heat and pressure lead to the formation of carbon molecules, which can result in cracks and inclusions within the diamond. Learn more about natural diamonds and how they are formed in our Natural Diamond Guide

Lab grown diamonds are also formed in intense heat and pressure, however this process is sped up so it only takes a few weeks. Lab grown diamonds can also form inclusions because of this, the more inclusions a stone has, the lower it will score on the clarity grading system.

4. How Clarity Effects the Diamonds Sparkle 

Diamonds graded below 'Slightly Included 1' may contain inclusions that can impact the diamond's sparkle. Heavy inclusions can disrupt internal light reflection, reducing the amount of light that exits the diamond and reaches the observer's eye. Therefore, only diamonds graded 'Slightly Included 2' and lower may exhibit diminished sparkle due to inclusions.

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