The Complete Guide to Diamonds

July 4, 2026

Introduction to Diamonds

Diamond is the hardest naturally occurring substance on Earth - formed over billions of years under specific levels of heat and pressure. These gemstones possess a combination of rarity, durability and - when skillfully cut - brilliance that give them timeless appeal.

These qualities make them perfect for use in jewellery. This is a gemstone built to be worn, loved and passed down for generations.

However, choosing a diamond can be a daunting prospect - so much terminology, a seemingly complex grading system and endless options in size and quality and cut - where do you start?

This guide is here to help. We'll walk you through everything you need to know about how to judge a diamond's quality and character - the 4Cs, the difference between natural and lab-grown stones and how to choose a shape that suits you. Whether you're shopping for an engagement ring or considering a bespoke piece designed entirely around you, this guide will break everything down and help give you the confidence to choose your perfect diamond.

What is a diamond?

Understanding where a diamond comes from is the first step to understanding its value.

For diamond to form, a specific set of conditions needs to occur. There must be a source of carbon where the carbon atoms are free to bond with one another without oxygen. If they do this where there are temperatures between 900 - 1,400°C and pressures of 40-80 kilobars, they form incredibly strong covalent bonds in a rigid crystal lattice - creating the hardest naturally occurring material known.

Scientists have estimated the depths and areas below the Earth's crust where they believe these conditions occur, however, they are far beyond our reach. Diamonds would be locked away indefinitely if it were not for volcanic activity. Eruptions carried diamonds up through the Earth's crust and deposited them where they could eventually be found and mined. Natural diamond formation is a remarkable process over billions of years.

Not every diamond on the market today has been formed in this way, however. Scientists have long been trying to create diamonds in the laboratory and now technology has advanced to the stage where gem-quality diamond can be created. The stones produced have the same chemical, physical and optical properties as those formed naturally in the earth. We'll explore what that means for buyers in more detail shortly.

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The Four Cs Explained

You might have heard people talking about 'The 4Cs' and it is often where a jeweller will start when taking customers through the qualities of particular diamonds.

The 4Cs - cut, colour, clarity and carat - are at the heart of the internationally recognised standard for assessing diamond quality. This was developed by the Gemological Institute of America (GIA) to give gemmologists, jewellers and buyers a universal system to accurately describe diamond quality.

Let's explore each of those elements.

Cut

A rough diamond isn't as bright and sparkly as the gemstone you probably have pictured in your mind. In order to unlock the spectacular light display associated with diamond, the gemstone must go through a process of cutting and polishing.

A well-cut diamond can produce mesmerising displays of brightness (the white light reflected back from the surface and inside of the gemstone), fire (the flashes of colour you can see) and scintillation (the contrasting areas of light and dark that you can see when you or the diamond moves - the sparkle).

A diamond with high colour and clarity grades can still look flat and lifeless if it's poorly cut, whereas a skilled diamond cutter can help even smaller stones outshine larger ones entirely. Cut is, therefore, crucial when you're looking to purchase a diamond.

Colour

You might be surprised to discover that diamonds come in many colours. We'll look first at the diamonds that are graded on the D to Z colour scale - those diamonds that are colourless (D) to those that have a noticeable yellow or brown tint (Z).

On this scale, the less colour, the better. Diamonds that are truly colourless are rare, which means that they can be significantly more expensive than those only a grade or two below. In practice, diamonds graded G-J are considered 'near-colourless' and still offer excellent quality without the price tag attached to the top grades. If you're working with a budget, this is one of the best places to make a compromise.

Diamonds that have enough colour to be classified as 'coloured diamonds' are rarer still and are graded using a different process. In this case, the more colour, the better.

Clarity

Clarity looks at the presence of 'clarity characteristics' which can be broken down into two categories - inclusions (internal or surface-reaching characteristics) and blemishes (surface characteristics).

These 'characteristics' might be things like mineral inclusions within the stone, small knocks or chips on the surface or more dramatic breaks that travel into the stone. Flawless diamonds - with no inclusions or blemishes visible under 10x magnification are very rare - most jewellers will never encounter one.

Diamonds with high clarity grades also come with high price tags. In practice, for most people, what's important is that the diamond is 'eye-clean' - meaning that you can't see the clarity characteristics without a jeweller's loupe. For stones under about two carats, a diamond graded VS2 or even SI1 would fall into this category and be a little kinder on your budget.

Carat

Carat is the measure of a diamond's weight. Some interpret this as size, however, it's not quite as simple as that. Two diamonds of identical weight can look very different depending on their cut.

When you're buying a diamond, it's important to know that prices jump noticeably at certain carat weights. These jumps occur at weights such as 0.50ct, 1.00ct and 1.50ct. If you're working with a budget, prioritise the quality of the cut over the carat weight and go for a diamond just under one of these thresholds (0.95ct rather than 1.00ct, for example). You'll see the effect of the cut whenever you look at the diamond, whereas the difference in size won't be noticeable.

Natural vs. Lab-Grown Diamonds

Many of the questions we're asked about diamonds today are about lab-grown diamonds. This is understandable due to the considerable changes to the diamond market in recent years.

As mentioned above, lab-grown diamonds have the same chemical, physical and optical properties as natural diamonds - they are just formed in a laboratory over a few days to weeks rather than naturally in the earth over billions of years. Specialist equipment is required to tell them apart - you can't tell the difference under a standard inspection.

So, what does this mean if you're looking to buy a diamond?

Price

Lab-grown diamonds are significantly less expensive than natural diamonds of equivalent size and quality. The technology used to create lab-grown diamonds has improved so much in recent years that lab-grown diamonds of significant weights are now available with excellent colour and clarity grades for a fraction of the price of an equivalent natural stone.

Value Over Time

Natural diamonds, particularly high quality stones, have historically held their value in a way that lab-grown diamonds are not. The reproducible nature of lab-grown diamonds means they are not good candidates for a piece of jewellery meant as an investment.

Diamond Shapes: Which one suits you?

Shape is often the first thing to decide on as it's the most visually obvious and has a big impact on how the final piece of jewellery will look. Here are the most popular options.

Round Brilliant

Most diamonds destined for jewellery are cut as round brilliants. This style, featuring 57 or 58 facets maximises light performance. If sparkle is the priority, these stones deliver.

Oval

The elongated silhouette of the oval can create the illusion of greater size and tend to appear a little more elegant than rounds when getting into the larger sizes.

Cushion

A square shape with rounded corners that you'll often find in older cuts. This shape is closer to the shape of the diamond rough and was easier to cut before diamond cutting technology had advanced. This shape is now prized for its romantic, vintage character.

Emerald

This classic step cut is timeless with its clean lines an elegant silhouette. This cut prioritises clarity over sparkle - the facet-arrangement means that inclusions will be more visible, so a good clarity grade matters here.

Pear

This teardrop silhouette combines the sparkle of a round brilliant with a distinctive, elongated shape.

Princess

A square shape with sharp, modern corners and plenty of sparkle.

Marquise

This narrow, elongated shape is elegant while maximising apparent size.

Asscher

This square step cut has a distinctive art-deco appearance and can look very striking in minimalist or vintage inspired pieces. Again, a high clarity grade is important.

There is no overall 'best' shape - only a shape to suit you, your taste and your personality. Do you like the clean lines of a step cut like an emerald or an asscher cut? Is sparkle your priority? Or do you want to go for a more unusual silhouette?

The overall design of the piece you want to create is also important. This is often where a bespoke approach comes into its own, since it can be difficult to picture a certain shape as a finished piece of jewellery without a design sketch or examples to guide you.

How to Choose a Diamond for Your Budget

So, now you're familiar with the terminology and know what to look out for, how do you use all of this information to choose the best diamond for your budget?

It's helpful to decide which of the 4Cs are most important to you.

If you're going for maximum sparkle, cut can actually be more important than carat. Prioritise an excellent brilliant cut and good colour and be ready to compromise on carat and clarity.
If you have your heart set on a particular carat weight, be flexible on clarity and go for a brilliant cut which will be better at hiding any visible inclusions than a step cut.
If you want to balance beauty and value, an excellent cut in the G-J colour range with a clarity grade of SI1 or higher is a great combination.
If character and individuality matter more to you than the 4Cs, look for vintage and antique cuts - perhaps an old mine cut or a rose cut - they may have visible inclusions but they have so much character and give you the chance to make your design all the more personal.

Certification & Authenticity

Any diamond of significant value should come with an independent grading report from a reputable laboratory - for natural stones this will commonly be the Gemological Institute of America (GIA). This report will detail the 4Cs, along with measurements, proportions and the stone's unique identifying characteristics.

This provides you with an independent, unbiased assessment of the diamond's quality as well as providing a clear record of the stone for insurance purposes. It would also prove useful should you ever decide to sell the stone.

If a stone doesn't come with grading from a recognised lab - this is not uncommon, especially for smaller diamonds - a trustworthy jeweller will always be happy to explain why.

Caring for Your Diamond Jewellery

Diamonds may be the hardest natural substance on Earth, however, they're not indestructible. A sharp knock at the wrong angle can chip or break a stone. Settings can also show signs of wear over time which might result in a stone coming loose. However, a little routine care can keep a piece looking its best for decades - here are some tips.

Unfortunately diamonds love grease and the oils from cosmetic products and even your skin can dull the sparkle. Luckily, a quick, gentle scrub with a soft toothbrush, warm water and a gentle dish soap sorts this out.
While they won't damage diamonds, certain cleaning products and chlorine can damage the metal of its setting - take your diamond jewellery off before using any harsh chemicals, going swimming or using a hot tub.
As diamonds are at 10 on the Mohs scale, they can scratch every other gemstone as well as other diamonds. When you're storing your diamond jewellery, make sure you store it separately, ideally with each piece in its own box or pouch.
It's a good idea to take any jewellery that you wear often, particularly the pieces you wear every day, to be checked by a jeweller. For things like engagement rings, this might be an annual thing. They will check the stones are still secure in their settings and should give the piece a clean and a polish for you at the same time to get it back to its sparkly best.

Bespoke Diamond Commissions

If you're ready to start using your new diamond knowledge to choose your perfect diamond for a unique piece of jewellery, we would love to help.

Whether you're designing an engagement ring, reimagining a design for a family stone, or creating something special for your self, we can guide you through the process. Find out more about our process for commissions on our bespoke page and, when you're ready, get in touch.

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Diamond FAQs

Which is the most important of the 4Cs?

It's best to look at the 4Cs together rather than choosing a diamond based on one of these elements of diamond quality. However, the factor with least room for compromise is cut. It usually has the greatest impact on how a diamond looks, regardless of colour, clarity or carat.

Is a lab-grown diamond a 'real' diamond?

Yes - lab-grown diamonds share the same chemical, physical and optical properties - the difference is origin.

How much should I spend on an engagement ring?

There's no fixed rule and conventions such as 'two month's salary' were born of marketing campaigns and shouldn't be used as guidance. You might be more comfortable setting a realistic budget and then seeing what that gets you in terms of quality - using the 4Cs as a guide.

Will a smaller, well-cut diamond look better than a larger, poorly cut one?

Usually, yes. An excellent cut will produce a much better display of light, making the stone appear more brilliant - and sometimes larger - than a bigger diamond with poor proportions and polish.

How do I know my diamond is genuine?

If you don't have a certificate, you can take your diamond to a jeweller. Many have diamond testing tools in their workshops. If you want further reassurance, you can arrange for independent certification from a lab like the GIA - however, bear in mind that the stone may have to be removed from its setting first if it is in a piece of jewellery.