Understanding the four C's: a guide to choosing your diamond
Choosing a diamond is exciting, but the letters, numbers and unfamiliar terms can make it feel a little daunting. You might know you love an oval diamond or a beautiful emerald cut but what should you actually look for?
This is where the four C's, cut, colour, clarity and carat weight can help. They describe a diamond’s qualities and give you a way to compare stones. Understanding them makes it easier to decide where to spend your budget and what matters most to you.
You don’t need to become a diamond expert. Here are some useful tips before choosing yours.
1. Cut: how your diamond interacts with light
When we talk about cut, it is easy to think we mean a diamond’s shape: round, oval, pear or emerald, for example.
Shape describes its outline. Cut quality describes how well its proportions and facets work together to interact with light. This affects its brightness, flashes of colour and sparkle as it moves.
A diamond can have a high colour and clarity grade, but still look less lively than you might expect if its cut does not make the most of the light.
For standard round brilliant diamonds in the D-to-Z colour range, GIA gives an overall cut grade from Excellent to Poor. Other shapes, such as ovals, pears and emerald cuts, are not covered by that same GIA overall cut grading system. Their appearance needs to be assessed individually.
Different cutting styles also have different personalities. An emerald or Asscher cut offers broad flashes of light and a more open, geometric appearance; a brilliant cutting style creates a different pattern of sparkle.
My advice: give the diamond’s appearance plenty of attention. Look at how it behaves as it moves, rather than choosing from a list of grades alone. If we are working together, I can provide you with an image and video of the diamond we are recommending for you so as you can make a fully informed decision.
2. Colour: how much tint is present
For diamonds assessed on the usual D-to-Z scale, colour grading measures the absence of colour.
The scale begins at D, with increasing amounts of tint as it moves towards Z.
| Colour grades | Description |
|---|---|
| D–F | Colourless |
| G–J | Near colourless |
| K–M | Faint colour |
| N–R | Very light colour |
| S–Z | Light colour |
The differences between neighbouring grades can be subtle. Diamonds are graded under controlled conditions, rather than simply judged as they sit in a ring.
A higher colour grade is not automatically the best choice for your taste. You may love an icy appearance, or find yourself drawn to a little warmth.
The shape, size and setting also influence how you experience the colour, so I would always consider the stone as part of the finished design.
Naturally coloured diamonds, such as fancy pinks and yellows, are assessed differently from diamonds on the D-to-Z scale.
My advice: You may find that a subtle difference on paper makes very little difference to what you enjoy looking at.
3. Clarity: the characteristics within and on a diamond
Diamonds can contain internal characteristics called inclusions and surface characteristics called blemishes.
Clarity grading considers their size, number, position, nature and how noticeable they are under 10× magnification.
The main clarity categories are:
| Grade | What it means |
|---|---|
| FL — Flawless | No inclusions or blemishes visible to a skilled grader at 10× magnification |
| IF — Internally Flawless | No inclusions visible at 10×; surface blemishes may be present |
| VVS1–VVS2 — Very, Very Slightly Included | Inclusions are very difficult to see at 10× |
| VS1–VS2 — Very Slightly Included | Minor inclusions visible with effort at 10× |
| SI1–SI2 — Slightly Included | Inclusions are noticeable to a skilled grader at 10× |
| I1–I3 — Included | Obvious inclusions at 10×, which may affect transparency, brilliance or durability |
Many clarity characteristics are too small to see with the unaided eye.
You may hear a diamond described as “eye-clean”, meaning its inclusions are not visible to the unaided eye under the viewing conditions being used. This is a descriptive term, rather than a formal clarity grade, so it is worth asking exactly what the seller means.
Two diamonds with the same clarity grade can look different because their inclusions sit in different places or are more noticeable in one stone.
My advice: you do not need a flawless diamond to have a beautiful diamond. Ask whether its characteristics affect what you can see, how it sparkles or its suitability for the setting. Indeed, some diamonds with multiple inclusions such as salt and pepper diamonds can be absolutley beautiful. Corinne is happy to source and work with any type of diamond or stone. Please see bespoke and make an enquiry.
4. Carat: how much your diamond weighs
Carat is a measure of weight, rather than a direct measurement of size.
One carat equals 0.2 grams. A carat is divided into 100 points, so a 50-point diamond weighs 0.50ct. This is different from the carat used to describe gold purity, as in 9ct or 18ct gold.
Two diamonds with the same carat weight can look different in size because of their shape and proportions. Some carry more of their weight in their depth, while others spread it across a wider visible surface.
It is also useful to distinguish between the weight of one diamond and total carat weight. A pair of earrings described as 1ct total weight might contain two 0.50ct diamonds. Always check what the description includes.
With natural diamonds, prices per carat often increase around familiar weights such as 1.00ct or 1.50ct. A stone just below one of these thresholds can be worth considering.
My advice: look at the measurements and how the diamond feels on you. A number cannot tell you whether you will love its proportions on your hand.
Which of the four Cs matters most?
There is no single combination that is right for everyone.
I would usually begin with the shape and appearance you love, give careful attention to cut quality, and then balance colour, clarity and weight within your budget.
For example, you might prefer a slightly smaller diamond with a beautiful play of light. Or you may be happy with a little warmth in the colour if it allows you to choose the proportions you love.
The aim is to understand which differences you will notice and appreciate, rather than pay for the highest possible grade in every category.
Do the four Cs apply to laboratory-grown diamonds too?
Cut, colour, clarity and carat weight are relevant to both natural and laboratory-grown diamonds. Laboratory-grown diamonds can also have inclusions, colour variations and differences in cut quality.
However, reports do not all use the same format. GIA’s current assessment for colourless to near-colourless laboratory-grown diamonds uses Premium and Standard categories, rather than the individual colour and clarity grades used on its natural diamond reports.
When comparing diamonds, ask which laboratory issued the report and what its terminology means.
Choosing a diamond you will love wearing
The four Cs are a useful starting point, but they cannot describe everything you will love about a diamond.
It's shape, the way it catches the light, it's setting and the meaning behind it all play a part. A report helps explain the stone; seeing it helps you discover how you feel about it.
At Lulu & Boo, I want you to feel comfortable asking questions and confident in your choice.
If you are thinking about a diamond piece, get in touch. We can explore the options together and find a balance of beauty, budget and design that feels right for you.