Diamond Grading
What jewellery buyers must know about diamond quality
Every diamond tells its own story. Just as each person has their own unique fingerprint, diamonds hold their own distinctive characteristics, whether you’re talking about blue diamonds from Lesotho, fancy yellows or pinks from Australia, or exquisite white diamonds from South Africa.
The Gemological Institute of America (GIA) created the 4Cs – Cut, Clarity, Colour and Carat weight – as the universal method for assessing diamond quality.
Diamond cuts and grading
When you look at a sparkling diamond, you might think its shape determines how it catches the light. But there’s actually a fascinating science behind that sparkle. While we often hear about round, oval, or pear-shaped diamonds, the ‘cut’ refers to something entirely different – the arrangement of 58 tiny surfaces called facets that interact with light.
Each rough diamond presents unique characteristics that influence how it should be cut. Much like wood has a grain, diamonds have natural structures that master cutters must work with, not against. These decisions aren’t just about maximising size – they’re about finding the right balance between the stone’s natural features and its final beauty.
“In diamond cutting, we look for proportions between 55% and 65%,” explains Mark Gieljoumie, GIA-certified Gemologist at The Diamond Works. “The stone’s depth from its flat top to pointed bottom should ideally be about 60% of its width. This balance between the crown (top), pavilion (bottom), and girdle (middle) determines how light moves through the stone.”
Each diamond at The Diamond Works undergoes careful assessment on the GIA grading scale from Excellent to Poor. While not every diamond will achieve a perfect cut – nor should it – each stone is evaluated for how well its proportions allow it to interact with light. Natural inclusions (internal characteristics) also play a role, with cutters positioning them thoughtfully to maintain the stone’s beauty and durability.
This careful balance of technical skill and artistic judgment ensures each diamond’s unique characteristics shine through in its final form.
Diamond clarity and grading
GIA diamond clarity grades range from Flawless to Included:
- Flawless (FL)
- Internally Flawless (IF)
- Very, Very Slightly Included (VVS1 and VVS2)
- Very Slightly Included (VS1 and VS2)
- Slightly Included (SI1 and SI2)
- Included (I1, I2 and I3)
These grades assess the natural characteristics within the diamond, including surface blemishes and internal inclusions (or flaws). For Gieljoumie, a natural diamond’s inherent features, including slight inclusions, actually make each stone distinctive rather than diminishing their value.
“At the one end of the diamond grading scale you get flawless diamonds, but these are very rare. At the other end of the scale are diamonds with inclusions that can be seen with the naked eye,” explains Gieljoumie. “But all have value, and I love each stone’s unique DNA.”
Diamond colour and grading
The diamond colour scale runs from completely colourless (D) to light yellow (Z). Think of it as shades of white – from pure white paper to a slightly warm tone. South African diamonds are famous for their exceptional whiteness, typically falling in the most prized D to G range.
“South Africa’s unique geology gives us our famous white diamonds. The absence of nitrogen in our soil means our diamonds stay pure and colourless – that’s what makes South African diamonds special.”
– Mark Gieljoumie, GIA-certified Gemologist at The Diamond Works”
Brightness
Brightness – often called brilliance – is the effect of all the diamond’s internal and external reflections of white light, best observed under diffused lighting. Well-cut diamonds are brighter than poorly fashioned ones, even if they’re of equivalent size, color and clarity. In general, the brighter a diamond is, the higher its grade will be.
Fire
Fire results when white light traveling through the diamond is dispersed into its rainbow of spectral colors. Look for red, blue, yellow or orange flashes as you rock and tilt it under store spotlights.
Scintillation
Scintillation is a combination of sparkle and pattern. Sparkle refers to the spots of light that flash when the diamond, you or the light source moves. In an attractive diamond, the reflections should appear even and balanced in size.
Pattern
Pattern is the relative size, arrangement and contrast of bright and dark areas that result from a diamond’s internal and external reflections. There must be enough contrast between the bright and dark areas to give the pattern a crisp, sharp look, but no distracting dark areas.
Diamond carats and grading
The word ‘carat’ has an interesting story – it comes from measuring diamonds against carob seeds centuries ago! Today, one carat is exactly 0.2 grams, giving us a precise way to weigh these precious stones.
But here’s what really matters: size is just one part of what makes a diamond special. At The Diamond Works, we guide our clients to look at the complete picture. A smaller diamond with excellent cut, colour and clarity can be more striking than a larger stone of lower quality.
Think of it this way – while larger diamonds naturally cost more (if they share the same quality features), the perfect diamond for you might not be the biggest one in the showcase. What matters most is finding a diamond that captures your heart and matches your style.
Diamond grading and the GIA
Think of a GIA certificate as your diamond’s passport – it’s an official document that tells you everything about your stone. The Gemological Institute of America (GIA) is the most trusted name in diamond certification worldwide.
Your GIA certificate confirms:
- Your diamond's exact qualities (cut, colour, clarity, and carat weight)
- Its size measurements
- Any unique marks inside the stone
- That it's a natural diamond, not a synthetic one
Visit us at The Diamond Works in Cape Town, where our GIA-certified gemologists will walk you through how diamonds are graded, helping you understand exactly what makes each stone unique.
Book a Sparkling Tour at The Diamond Works
FAQS
What are the grades in diamonds?
Diamonds are graded according to the GIA 4Cs: Cut, Clarity, Colour and Carat weight. Each ‘C’ (with the exception of carat weight) has its own grading. For example, the colour scale runs from D to Z, while the GIA grading system rates cuts as Excellent (EX), Very Good (VG), Good (G), Fair (F) and Poor (P).
What are G colour diamonds?
A G colour diamond represents excellent value, sitting in the near-colourless range while maintaining an icy white appearance. South African diamonds are particularly renowned for their exceptional white colour grades (D to G).
What does VVS mean in diamond grading?
Your diamond will receive a GIA Clarity Grade. VVS stands for ‘Very, Very Slightly Included’ (VVS1 and VVS2). As flawless or internally flawless diamonds are so rare, VVS graded stones are among the most valuable diamonds you can find.
What is the highest-class diamond?
According to the GIA Clarity Scale, Flawless (FL) diamonds are the highest grade. It means the diamond has no inclusions or blemishes (visible under 10x magnification).