Diamonds explained

Understanding diamonds is an essential part of choosing or designing a diamond ring, but how do you know which stone to choose? What even makes one diamond better than another? How do you know you’re making the right choice? Let our expertise guide you...

Our comprehensive Diamond Guide is here to illuminate key facets of the diamond selection process.

We'll help you make an informed choice that shines as brightly as your love, based on both fact and feeling.
Rob Sherwin
Diamond Specialist and Lead Designer

The 4Cs in Brief

  • 1. Carat Weight

    1. Carat Weight

    Carat denotes the weight of a diamond. While the other aspects mentioned here have a bearing on diamond quality, the carat weight doesn't, and is simply a measure of weight.

    There are 100 points in a single carat, so a diamond weighing 3/4 carat would be a '75 point diamond'. Diamonds of 0.30 - 0.75 carat are very popular for their size and value. Large diamonds are rarer and therefore more valuable than small ones.

  • 2. Diamond Cut

    2. Diamond Cut

    Many people think of a diamond’s cut as shape (round, princess cut, oval diamond, pear shape etc), but what diamond cut actually means is how well a diamond’s facets reflect and scatter light and sparkle.

    The grade of cut, developed by the Gemological Institute of America (GIA), also takes into account factors like the weight relative to diameter, the girdle thickness (which in turn affects its durability), symmetry and polish of the facets.

  • 3. Diamond Colour

    3. Diamond Colour

    The ideal diamond is completely colourless. But even if it appears colourless, a stone may actually have slight tones of yellow or brown. The GIA grades colour alphabetically from D (colourless) to Z (heavily tinted).

    However grades D to F are considered colourless and G to J near colourless. Some colour distrinctions are so subtle that they're not noticeable. Diamonds with a D grading are the most valuable, although price will still be affected by many other factors.

  • 4. Diamond Clarity

    4. Diamond Clarity

    Natural diamonds are the result of carbon exposed to extreme heat and pressure deep underground, resulting internal characteristics called inclusions. Many of these won't be visible to the naked eye.

    Evaluating diamond clarity involves determining the number, size and position of inclusions and how they affect the appearance of the stone. The closer to flawless, the better its clarity, and this will be reflected in the price.

Expert tip

Be sure to consider the diamond qualities along with other key aspects such as the ring setting, the wearer's lifestyle and fashion preferences, and most importantly - how the design makes them feel.

More about ring design

Beyond the 4Cs

  • 5. Fluorescence

    5. Fluorescence

    Fluorescence is the glow you sometimes see when an object emits visible light. Some diamonds do this when they are exposed to long-wave ultraviolet (UV) rays from sources like strong sun or nightclub lighting.

    This can cause them to emit a bluish light or occasionally a different colour light. Once the UV light source is removed, you no longer see this glow. Diamond fluorescence is neither good nor bad. Some people find fluorescent diamonds beautiful and fascinating—others may not.

  • 6. Certification

    6. Certification

    The two most popular certification bodies are Gemological Institute of America (GIA) and International Gemological Institute (IGI). Both are well respected diamond grading institutions.

    However, GIA tends to be more popular in the USA, while IGI is also very popular in Europe and Asia. IGI often offers faster and cheaper certifications. Many diamonds purchased from a diamond dealer or retail jeweller will already come with either one of these certificates included.

  • 7. Diamond Origin

    7. Diamond Origin

    As the world leader in gemological research, GIA is uniquely able to utilise over 60 years of scientific knowledge and technology to deliver the rough-to-polish matching confirmation for polished stones. GIA collects data and images for rough analysis.

    Once GIA receives the polished diamond, GIA uses markers and data identified during the analysis of the rough to scientifically match the polished diamond to its original rough, confirming the diamond’s country of origin, often displayed on the diamond certificate.

  • 8. Created Diamonds

    8. Created Diamonds

    As a material, there is no chemical difference between lab grown diamonds and organically grown diamonds. They are identical terms of physical appearance and properties.

    In fact, it has only been recently that testing tools could tell the difference between laboratory grown diamonds and diamonds mined from the earth. The differences are in where it's made (including environmental and social impacts), product cost, and resale value of the diamond, which is considerably lower for lab grown diamonds.

Diamond shapes

Sometimes referred to as diamond cut, the shape of your diamond refers to the general silhouette of the stone rather than the quality of cut and arrangement of facets you read about in the 4Cs. In no particular order, here are some of the most popular diamond shapes to consider for ring.

  1. 1

    The round cut is arguably the most recognisable diamond shape for an engagement ring. Virtually all round diamonds are brilliant-cut to enhance their fire and sparkle. A great all-rounder!

  2. 2

    Oval diamonds have skyrocketed again in popularity recently, having first been seen as early as 1304. With similar fire and brilliance to round cut, they are elongated which increases the surface area and gets you a larger looking diamond for its weight.

  3. 3

    Princess cut diamonds are another popular choice. Distinctively chic with its clean square shape, we'd call this diamond shape a modern classic. Many people opt for a prong setting to protect its four corners yet still let plenty of light through.

  4. 4

    Emerald cut diamonds get their unique art-deco look from the step cuts which produce a stunning hall-of-mirrors effect. The long lines create brightness and shine and give the emerald cut an elegant appeal and luxurious glamour of a bygone era.

  5. 5

    The pear or teardrop diamond is a statement look which is also gaining popularity. Partly thanks to their elongated shape, pear cuts look larger than a round diamond. And similar to the oval, they are actually larger on the surface, giving you more visible diamond for your money.

  6. 6

    There's a whole host of other diamond shapes to consider, particularly if you're looking for a unique statement engagement ring. Marquise, Asscher, Cushion cut and even heart shaped diamonds are all contenders for something a little different.

Diamond buying guides

Still deciding on the shape and cut of diamond for your engagement ring? Find out more about these stunning and timeless styles in our diamond buying guides:

Round Brilliant Cut Diamond Buying Guide: What to Know

Ultimate Oval-Cut Diamond Buying Guide: Tips & Insights