Diamond Buying Guide
Everything you need to choose a diamond with confidence: how diamonds are graded, how natural and lab-grown diamonds compare, and what to look for in fine diamond jewellery.
The four Cs
Every diamond is described by four characteristics, known as the four Cs. Together they are the universal language for describing diamond quality. No single C decides how beautiful a diamond is. It is the balance between them that matters.
1. Cut
Cut is the grade that has the greatest influence on a diamond's beauty. It describes how well a diamond's proportions, symmetry and polish return light to the eye, creating brilliance (white light), fire (flashes of colour) and scintillation (sparkle as it moves). A well-cut diamond can look larger and brighter than a heavier stone with a poor cut.
| Grade | What it means |
|---|---|
| Excellent | Maximum brilliance and fire. Light is reflected back through the top of the stone. |
| Very Good | Very high brilliance, with a difference from Excellent that is hard to see without training. |
| Good | Reflects most light that enters. A good balance of beauty and value. |
| Fair and Poor | Noticeably less sparkle, as light escapes through the sides or bottom. |
2. Colour
Diamond colour is graded on a scale from D to Z, based on how little colour the stone shows. D is completely colourless and the rarest. Towards Z, diamonds show an increasingly visible yellow or brown tint. The differences between neighbouring grades are subtle and usually only visible side by side under controlled lighting.
| Grade | Description |
|---|---|
| D, E, F | Colourless. The purest and rarest white. |
| G, H, I, J | Near colourless. Appears white to the eye once set, especially in white gold. |
| K, L, M | Faint. A slight warmth is visible, which can suit yellow gold. |
| N to Z | Very light to light. A visible yellow or brown tint. |
Metal colour plays a part too. White gold complements the whitest grades, while yellow gold is more forgiving of a faint warmth.
3. Clarity
Most diamonds contain tiny natural features, called inclusions inside the stone and blemishes on the surface. Clarity grades describe how many there are, how large and where they sit, judged under 10x magnification. Many are invisible to the naked eye, so a diamond can be "eye-clean" without being flawless.
| Grade | Description |
|---|---|
| FL, IF | Flawless and Internally Flawless. No inclusions visible under 10x magnification. Extremely rare. |
| VVS1, VVS2 | Very, very slightly included. Inclusions are very difficult to see even under magnification. |
| VS1, VS2 | Very slightly included. Minor inclusions under magnification, normally invisible to the eye. |
| SI1, SI2 | Slightly included. Inclusions are noticeable under magnification and sometimes visible to the eye. |
| I1, I2, I3 | Included. Inclusions are visible to the eye and can affect brilliance. |
4. Carat
Carat is a unit of weight, not size. One carat equals 0.2 grams and is divided into 100 points, so a 0.50 ct diamond can also be called a 50-point diamond. Larger diamonds are rarer, which is why price rises faster than weight. How large a diamond looks also depends on its cut and shape. As a guide, a well-cut round brilliant diamond measures approximately:
| Carat | Approx. diameter |
|---|---|
| 0.25 ct | 4.1 mm |
| 0.50 ct | 5.1 mm |
| 0.75 ct | 5.8 mm |
| 1.00 ct | 6.5 mm |
| 1.50 ct | 7.4 mm |
| 2.00 ct | 8.1 mm |
In earrings and tennis bracelets you will often see the total carat weight (ct tw). This is the combined weight of every diamond in the piece, or in both earrings of a pair.
Natural and lab-grown diamonds
We offer both, because both are real diamonds. They share the same chemical composition, hardness and optical properties, and they are graded on the same four Cs. Even a trained gemmologist cannot tell them apart without specialist laboratory equipment.
| Natural | Lab-grown | |
|---|---|---|
| Material | Pure crystallised carbon | Pure crystallised carbon |
| Hardness | 10 on the Mohs scale | 10 on the Mohs scale |
| Origin | Formed deep in the earth over billions of years | Grown in a controlled environment |
| Rarity | Finite and rare | Not limited by nature |
| Price | Higher for the same four Cs | Lower for the same four Cs |
The choice is personal. A natural diamond carries the rarity of something formed by the earth. A lab-grown diamond lets you choose a larger or higher-grade stone for the same budget. Whichever you choose, it will never change in colour or brilliance, which is why every diamond we set comes with our Lifetime Diamond Guarantee.
Grading reports
A grading report, sometimes called a certificate, is an independent assessment by a gemmological laboratory. Every piece comes with a jewellery report card: from IGI for lab-grown diamonds and from HRD Antwerp for natural diamonds in earrings and bracelets. The natural centre diamond of a ring comes with its own diamond certificate from GIA or IGI. Reports for lab-grown diamonds also confirm their laboratory-grown origin.
The report card describes the diamonds in your piece as a whole. Small diamonds, like those set in tennis bracelets, are not graded one by one. This is standard across the jewellery industry.
Choosing your gold
Our pieces are made in 9K, 14K and 18K gold. The karat tells you how much pure gold the alloy contains:
| Karat | Pure gold | Character |
|---|---|---|
| 18K | 75.0% | The richest colour and the most precious alloy. |
| 14K | 58.5% | A balance of rich colour and everyday durability. |
| 9K | 37.5% | Hard-wearing and the most accessible choice. |
Yellow gold has a warm, classic tone. White gold is gold alloyed with white metals and is often finished with a rhodium plating for a bright white surface, which can be renewed over the years.
Choosing diamond jewellery
Earrings
For diamond studs, the size of the diamond has the greatest effect on how they look when worn. Because earrings are seen from a distance, near-colourless grades and eye-clean clarity look beautifully white and bright.
Tennis bracelets
A tennis bracelet is a continuous line of diamonds, so consistency matters most: the stones should be well matched in colour and size for an even line of light. Look at the total carat weight and the security of the clasp. Our 4-year warranty covers clasps and settings against manufacturing defects.
Need help choosing?
We are happy to help you find the right diamond and piece. Reach us through our contact page, or explore our earrings and tennis bracelets.
