The Four C’s, cut, colour, clarity, and carat are the universal standard for evaluating a diamond. Established by Robert M Shipley, founder of the Gemological Institute of America (GIA), this system ensures consistency and accuracy in diamond grading, allowing consumers to make informed purchasing decisions.
Why was the four c’s developed:
Robert M Shipley established GIA, Gemological Institute of America in 1931 to provide formal gemological training to jewellers. The Four C’s were developed by Shipley to act as a universal scale to evaluate the characteristics of diamonds. Before the Four C’s, jewellers used a variety of terms such as A, AA, AAA, or the terms “without flaws” or “without imperfections”. These inconsistent descriptions made it difficult for consumers to compare diamonds and for jewels to communicate quality effectively.
As GIA states, without strict standards, the characteristics, quality, and value of a diamond would be left open to interpretation.
Carat:
Carat refers to the weight of the diamond, not the size. One carat is equal to 0.2 grams or 200 milligrams. Diamonds are measured to a hundredth of a carat for precision. While carat weight is a key factor in determining a diamond’s price, it does not directly tell you how large or visually impactful the diamond will appear. The weight of the diamond is one element in its overall appearance.
Carat vs perceived size:
The way the diamond has been cut influences how large the diamond appears. A well cut diamond will reflect light more efficiently and appear bigger, even with a smaller carat weight. Shape also affects how carat weight is distributed across the diamond’s surface. Certain shapes like oval or pear tend to appear larger than other shapes of the same carat weight because they have a larger surface area to depth ratio. This means between two diamonds that have the same carat weight, one may appear bigger, depending on how the weight is spread across the stone.
Cut:
Cut refers to how well the diamond interacts with light, influencing its brilliance and sparkle. Only round brilliant diamonds can be assigned a cut grading, this is because they have a standardised facet pattern that allows for consistent evaluation of how well light interacts with the stone. According to GIA’s standardised cut grading system, diamonds are evaluated on a 10-point scale ranging from Poor to Ideal, taking into account the following:
Components of a diamonds cut:
- Brightness: The total light reflected from a diamond
- Fire: The dispersion of light into the colours of the spectrum
- Scintillation: The pattern of light and dark areas and the flashes of light, or sparkle, when a diamond is moved.
- Weight ratio: How efficiently the diamond’s weight is distributed to maintain it’s proportions
- Durability: Resistance to damage based on its proportions and design (a thin culet can lead to easy damage and breaking)
- Polish: The smoothness of the diamond’s surface, including scratches, nicks and chips.
- Symmetry: Alignment and shape of a diamond’s facets.
IGI grades cut from fair to ideal.
Why does cut matter:
If a diamond’s cut is too shallow, deep or out of proportion, light can leak out of the lower facets of the stone instead of reflecting back to the viewer. This results in reduced sparkle and brilliance, making the diamond appear dull or lifeless.
A common misunderstanding is confusing cut with the shape of the diamond. For example, people will refer to an “oval cut” diamond, but this is incorrect. Oval is the shape, as the cut refers to the quality of the diamond’s proportions, symmetry, and polish, not its shape.
How to evaluate diamonds not given a cut grading?
For fancy shaped diamonds (all other diamond shapes that are not round brilliant), we look at the table and depth percentage. These measurements reveal how well the diamond has been cut in terms of its proportions, the ratio to its height and width. This influences the diamond's brilliance and sparkle by determining how the light interacts with the stone.
Colour:
Colour refers to the absence of visible colour in a diamond, with the grading scale measuring from D colours to Z. The clearer and more colourless the stone is, the more valuable, rare, and expensive the diamond is going to be. Diamonds beyond the Z range are classified as fancy colour diamonds. Diamonds are measured on colour from the culet up.
Robert M Shipley, began the colour grading scale at D to avoid association with the old methods of colour grading.
Colour is measured in a 10 point scale:
D - F: Colourless (0.0 - 1.0)
- Highest grade, diamonds will appear to have no colour in any setting.
- Diamonds without colour are extremely rare.
G - J: Near colourless (1.5 - 3.0)
- These diamonds have little colour
- When mounted in jewellery these diamonds will appear colourless
K - M: Faint (3.5 - 4.5)
- These diamonds have visible colour.
- Smaller diamonds less than 0.5 carat may appear colourless or near colourless when in jewellery.
N - R: Very Light (5.0 - 7.0)
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Noticeable colour that becomes more apparent when set in jewellery
S - Z: Light (7.5 - 10)
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Visible hue or tone
Fancy colour diamonds
These fall outside the D-Z category, fancy colour diamonds are colours beyond the Z range which display notable colour when viewed face up. These diamonds show colours such as blues, pinks, greens and more, caused by specific trace elements or structural anomalies. Unlike colourless diamonds, where less colour is more valuable, the value of fancy colour diamonds increases with the intensity and purity of their colour.
Assessing diamond colour from online photos and 360 degree videos
It’s impossible to accurately determine a diamond’s colour or detect subtle undertones, such as grey, brown or blue, without examining the diamond in person. While 360-degree videos and photos on diamond websites can provide a sense of choosing your diamond, they are highly inaccurate and fail to reveal the details.
This is a diamond we ordered from a large popular ecommerce website. This is the video that was displayed.
This is the diamond that arrived
How is colour measured:
Diamond colour is done under controlled lighting conditions using a set of master stones as benchmarks. Colourless diamonds are extremely rare in nature. Colourless diamonds allow more light to pass through, enhancing their brilliance and sparkle. Even subtle hints of colour can affect how light reflects and refracts within the diamond.
How are diamond colour, size, shape and setting related?
Size: The colour of a diamond is more noticeable in larger stones. As the size of the diamond increases, the table becomes larger, making any visible colour more apparent.
Shape: Diamond shape also impacts how colour appears. Stones with larger facets, like emeralds, ovals or radiant cuts can display more visible colour than shapes with smaller facets, like the round brilliant.
Setting: The metal in the ring setting can impact the appearance of the diamond’s colour. A diamond with a faint colour (K-M) may appear more colourless when set in white gold or platinum, as these metals compliment its tone. Compared to set in yellow gold, the warmth of the metal can accentuate the diamond's colour, making any hue more noticeable.
Clarity:
Clarity assesses the presence of inclusions (internal flaws) and blemishes (surface flaws), the fewer imperfections, the higher the clarity grade. According to GIA, “diamonds are assigned clarity grades ranging from Flawless (FL) to diamond with obvious inclusions (I3)”. The grade is based on the number, size and location of the inclusions and blemishes.
Evaluating diamond clarity requires 10x magnification to detect even the smallest imperfections that may not be visible to the naked eye.
Different diamond shapes can affect how different clarity gradings look. For example, round brilliants can sometimes hide minor inclusions, compared to an Emerald where inclusions with the same clarity grading may be more noticeable due to the open facets.
Clarity Grading:
Flawless:
- No internal or external characteristics
- Less than 1% of all diamonds are FL clarity
Internally flawless:
- Some small surface blemishes may be visible under microscope on IF diamonds
- IF diamonds have no inclusions within the stone, only on the surface
- Visually eye clean
Very Very slightly included:
- Minuscule inclusions that are difficult even for trained professionals to see under 10x magnification
- Eye clean appearance:
Very slightly included:
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Minor inclusions ranging from difficult to easy to see under 10x magnification
Slightly included diamonds:
- Inclusions are noticeable under 10x magnification
- Detectable by the eye
Included diamonds:
- Obvious inclusions
- Visible by the eye
- Henry Francis does not sell Included diamonds
Types of Inclusions:
- Bruise: Damaged diamond from impact that causes root like lines on the inside of the diamond. Bruises can affect the structural integrity of the diamond
- Chip: A small, shallow opening on the surface of a diamond often found near the girdle, culet or facet junctions.
- Cavity: A large or deep opening in the diamond's surface
- Knot: Cluster of diamond material that extends from the diamonds interior to the surface
- Graining: Irregularities in a diamonds crystal lattice structure
- Feather: Internal fractures, looks like a feather
- Crystal: A mineral crystal contained in the diamond.
- Pinpoint: Shiny or microscopic crystals within the diamond
- Cloud: Numerous pinpoint inclusions that may be too small to be distinguished individually and give it a cloudy, hazy appearance
- Needle: A thin crystal that looks like a tiny needle
- Twining Wisp: Complex, they form when multiple crystal growth directions intersect within a diamond.
- Indented Natural: Occur when the rough diamond's natural surface is not entirely removed during the cutting and polishing process. These inclusions may appear as depressions or rough patches on the diamond's surface
- Internal Laser Drilling: Laser drilling within a diamond that creates a surface-reaching feather. This then provides access for bleaching to decrease the visibility of inclusions
- Bearded Girdle: occurs when improper bruting (which is cutting a diamond to make the girdle round) which cause hair-like inclusions to form across the diamond's girdle area
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Laser Drill-hole: A tiny, surface-reaching tunnel produced by a laser light beam.
Types of Blemishes:
- Abrasion: Minute nicks along the facet junctions of a diamond, giving it a fuzzy appearance
- Extra facet: A facet that's not required by that diamond shape
- Lizard Skin: Wavy or bump area on the surface of the polished diamond
- Natural: Portion of natural rough diamond left on a fashioned stone
- Nick: Small notch
- Pit: Small opening that looks like a tiny white dot
- Polish: Parallel grooves and ridges left by polishing
- Burn Mark: Hazy surface that results from excessive heat during polishing
- Rough Girdle: irregular or granular girdle surface
- Scratch: A thin, dull white line across the diamonds surface
- Surface graining: Graining on the surface
How Inclusions form:
Inclusions and blemishes occur during the formation of a diamond.
Causes of inclusions in natural diamonds:
- Trapped minerals
- Internal stress
- Growth patterns
- Natural radiation
Causes of inclusions in lab diamonds:
- Imperfect seeds
- Trapped gasses or metals
- Added trace elements
- Growth irregularities
- Post-growth treatment
- Temperature changes
Diamond Treatments: Enhancing Appearance and Colour:
Diamonds can undergo treatments to improve their appearance, clarity or colour. There are two types of treatment: Permanent and Non-Permanent. GIA does not grade diamonds with non-permanent treatments as their effects are not stable and long-lasting. For diamonds with permanent treatments, GIA will disclose in their report the treatment type.
Permanent treatments are lasting and do not typically affect the diamond's structure. Examples include laser drilling, HPHT and irradiation.
Non-Permanent treatments are temporary and may require maintenance or can degrade over time. Examples include fracture filling and coatings.
What is the 5th C?
The 5th C refers to confidence or “certification”. Certification from a trusted 3rd party such as IGI or GIA gives you peace of mind and assurance of the diamonds quality. At Henry Francis we only sell IGI or GIA certified diamonds.
It’s important to note that while the Four Cs provide valuable insights into a diamond’s quality, they do not independently determine the diamond’s price or act as a certification. A diamond’s value is influenced by a combination of factors, including market demand and the interplay of its unique characteristics.
The Four C’s provide a standardised framework for assessing diamonds, but they don’t account for every aspect that can affect a diamond’s appearance.
Is it better to have a bigger diamond or a better quality
When deciding between a larger diamond and one with better quality, it depends on personal preference and priorities. A larger diamond may appear more impressive due to its size, but a smaller diamond with better cut and quality can often appear more brilliant and sparkly, offering more visual appeal. If you're unsure what you are after, please reach out to us at Henry Francis for help.
What does VVS mean for diamonds
VVS (Very Very Slightly Included) diamonds have inclusions that are so tiny they are difficult to see even under magnification. These diamonds are considered excellent in terms of clarity.
What's more important, colour or clarity
Both colour and clarity are essential factors in diamond grading, but their importance depends on individual preference. Colour affects the diamond’s visual appeal, with colourless diamonds being the more valuable, while clarity impacts the internal perfection of the diamond. In some cases, a diamond with a slightly lower clarity but better colour may be more desirable.
