A diamond is usually chosen to mark something that matters: an engagement, an anniversary, a promise. As the centre stone of an engagement ring, it will be worn every day for years, through ordinary weeks as well as special occasions. It’s worth understanding what you’re looking at before you choose.
Start with the cut, because it decides how much a diamond sparkles. Then choose the size you want, and spend on colour and clarity only as far as your eye can see the difference. Ask for an independent IGI or GIA certificate, and decide whether a natural or a lab-grown diamond suits you better.
At Anupam, our engagement rings are set with natural or lab-grown diamonds, and the centre stones are certified by IGI or GIA. This guide takes each choice in turn. If you’re still deciding on the ring itself, start with how to find the right ring.
What are the 4Cs of a diamond?
The 4Cs are cut, colour, clarity and carat: four ways of describing a diamond, set out by the Gemological Institute of America (GIA) and used by grading laboratories around the world. A certificate records all four, so one stone can be compared fairly with another.
| The C | What it measures | The scale | What your eye notices |
|---|---|---|---|
| Cut | How well the stone is proportioned and polished | Excellent, Very Good, Good, Fair, Poor | Sparkle: how bright and lively it looks |
| Colour | How little colour the stone has | D (colourless) to Z (a visible tint) | Whiteness, mostly in larger stones and in platinum 950 or 18ct white gold settings |
| Clarity | The tiny natural marks inside and on the stone | Flawless and Internally Flawless, then VVS, VS, SI and I grades | Whether you can see any marks without magnification |
| Carat | Weight, not size (1 carat is 0.2 grams) | Counted in carats and points, 100 to the carat | Size, and the price |
Which of the 4Cs matters most?
Cut. It isn’t the shape of the stone but how well it has been proportioned and polished, and that decides how light travels through it. A well-cut diamond sends light back up through the top and looks bright and lively. A poorly cut one lets light leak out of the sides or the bottom, and looks dull even with a high colour and clarity grade.
A cut grade is mainly given to round brilliants. For other shapes, the polish and symmetry grades on the certificate tell you how well the stone has been finished.
Our advice: look for the top grades for cut, polish and symmetry, then see the stone for yourself. A certificate can’t tell you how a diamond looks on your hand.
Ask to see a stone in daylight as well as under the shop lights. Spotlights flatter every diamond; daylight is much closer to how it will look day to day.
What colour grade do you need?
Diamond colour is graded on a scale from D, which is colourless, to Z, which has a visible warm tint. The less colour a diamond has, the higher its grade and, as a rule, its price.
You need less than the chart suggests. A grade or two either way is very hard to see once a stone is set, and colour shows more in larger stones than in smaller ones.
The metal around the stone matters too. An 18ct yellow gold or 18ct rose gold setting reflects warmth into the diamond, so a slightly lower colour grade passes for a higher one. In platinum 950 or 18ct white gold, the stone has nothing to hide behind, and colour is easier to see. Our guide to how to choose a metal compares the options.
What clarity do you need?
Clarity describes the tiny natural marks inside a diamond and on its surface. The scale runs from Flawless and Internally Flawless, through VVS (very, very slightly included) and VS (very slightly included), to SI (slightly included) and I (included).
What matters is whether you can see the marks without magnification. In many stones, the VS2 and SI1 grades look clean to the naked eye, but it depends on the individual stone and where its marks sit, so ask to look closely. Paying extra for Flawless rarely shows once the diamond is on your hand.
The shape makes a difference here. Step cuts such as the emerald cut have long, open facets that show marks more readily than brilliant cuts do, so they suit a cleaner stone.
Does a higher carat weight mean a bigger diamond?
Not exactly. Carat measures weight, not size. One carat is 0.2 grams, and it divides into 100 points, so a 0.50ct diamond is a 50-point stone.
As a guide, a half-carat round brilliant measures about 5mm across and a one-carat round about 6.5mm. Two stones of the same weight can still look different sizes. A deep stone carries more of its weight underneath, where you can’t see it, so it looks smaller from above.
Price rises with weight, and heavier diamonds cost more per carat as well as more overall.
How does the shape change the look and the price?
Shape is a matter of taste, but it changes both how a stone looks and what it costs.
- Round brilliant: the most sparkle, and usually the highest price per carat, because more of the rough crystal is lost in cutting it.
- Oval: looks larger than a round of the same weight, and lengthens the finger.
- Cushion: soft, squared corners with a slightly vintage feel.
- Emerald cut: long, straight facets that flash like a hall of mirrors rather than sparkle.
- Pear and marquise: pointed ends.
- Princess: square, with sharp corners that a good setting protects with a claw at each corner.
If you’re torn between two shapes, try both on. The difference is much clearer on the hand than in a photograph.
What does a diamond certificate tell you?
A certificate, or grading report, is an independent laboratory’s description of one particular stone: its shape, measurements and carat weight, and its colour, clarity and cut grades. It also states whether the diamond is natural or lab-grown. It doesn’t give a price, and it isn’t a valuation.
If you’re checking a stone you already own, how to tell if a diamond is real covers it.
GIA and IGI
GIA, the Gemological Institute of America, is a non-profit that created the 4Cs and the D-to-Z colour scale. IGI, the International Gemological Institute, is a worldwide laboratory. Both grade natural and lab-grown diamonds.
Keep the certificate with your receipt. If you insure the ring, the valuer will find it useful, and it identifies the stone if the ring ever needs to be replaced.
Should you choose a natural or a lab-grown diamond?
Natural and lab-grown diamonds are the same material: the same carbon, the same hardness and the same sparkle. The difference is origin and price. A lab-grown diamond costs less for the same size and grades, so many people choose a larger or finer stone for the same budget. A natural diamond formed in the earth, in most cases over a billion years ago, and for some people that origin matters.
We sell both, and the trade-offs, including what each is worth if you sell it, are set out in lab-grown or natural diamonds.
Moissanite and cubic zirconia are different stones altogether, not types of diamond. Our engagement rings are set with natural or lab-grown diamonds, not moissanite, and moissanite, lab-grown or natural diamond explains how they compare.
How do you make your budget go further?
- Stop just short of the round number. Price jumps at half a carat and one carat, so a 0.90ct stone looks almost the same as a 1.00ct one and costs noticeably less.
- Consider an oval or a lab-grown diamond. Both give more look for the money.
For the wider question of budget, see how much to spend on an engagement ring.
Does a diamond need looking after?
Diamond scores 10 on the Mohs scale and is the hardest naturally occurring mineral, so it resists scratching better than any other stone. Hardness is only part of the picture, though. The setting, the claws that hold the stone and the way the ring is worn all affect how it lasts.
Have the claws checked from time to time, particularly on a ring you wear every day. A worn claw is easier to deal with when it’s spotted early, and claw work and re-tipping are done in our workshop in Ashford. Our guide to how to look after your jewellery explains what to check.
See them on your own hand
A chart only gets you so far. A diamond looks different on your hand, in daylight, beside the metal you’ve chosen. Browse our engagement rings or our lab-grown collection, or book a time with us in Ashford and we’ll look at some stones together, with their certificates beside them.
Tell us the shape you like, the size you have in mind and your budget, and we’ll show you where the money makes the most difference.
Frequently asked questions
Is a GIA certificate better than an IGI one?
Grading is a trained judgement, so the same stone can come out a grade apart at two laboratories. Compare the stones themselves as well as the paperwork.
How do I know the certificate belongs to the diamond?
Check that the shape, measurements and carat weight on the report match the stone. If the report number is laser-inscribed on the edge, ask to see it under magnification; it should match the number on the paper.
Do the small diamonds in a ring have certificates too?
Usually not. Certificates are normally issued for the centre stone, while the smaller diamonds on the shoulders or in a halo are described by the jeweller. An insurance valuation records them along with the rest of the ring.
Can a diamond chip?
It can. A sharp knock in the wrong place can chip it, most often at a point or a thin edge. A setting that protects the points is the best defence.
What is a bow-tie in a diamond?
It’s a darker shadow, shaped like a bow tie, across the middle of some elongated stones such as ovals, pears and marquises. It comes from the way light travels through the cut. The certificate doesn’t grade it, so look at the stone itself: some bow-ties are barely noticeable, while others catch the eye straight away.
