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 Hatton Garden Diamonds

Holts Gems are proud suppliers of GIA certified diamonds in Hatton Garden. Graded by the world’s most renowned, independent and not-for-profit grading laboratory, our diamonds are hand selected by our qualified gemmologists to suit each individual budget and personal requirements. Learn more about diamonds below.

The 4Cs

Diamond Pricing

Diamond Shapes


Responsibly Sourced


How to choose the perfect diamond.

We’re here to help you find the right diamond for your engagement ring. Our qualified gemmologists are on hand to find you the perfect diamond within your budget.

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Diamond Grading

 Learn about the 4Cs

Choosing a diamond for your engagement ring is a big commitment, but how do you know you’ve found the perfect stone? Before buying a diamond, we’d always recommend you have a good grasp of the 4Cs, and how a diamond’s characteristics are graded.

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When viewing diamonds, there are certain characteristics and grades you should prioritise over others - the most important being the cut grade of the diamond. At Holts Gems, we recommend you choose a diamond with the cut grade ‘excellent’, as this will appear the brightest, sparkliest and liveliest. You may be able to get away with a ‘very good’ cut grade. This is where an expert opinion can come in useful. Our experts hand pick a selection of diamonds for each client, based on their budget and preferences. Typically, our experts would disregard a ‘very good’ cut, but they know how to spot a diamond that exceeds its grade on paper.



Following the cut grade, colour is an important characteristic that can largely affect the beauty of a diamond engagement ring. As traces of nitrogen are present in most diamonds, they can appear yellowish or brownish in tone. Diamond colour is graded from D-Z, D being the most colourless grade. Stick between D and F for a diamond that is bright and white. If you’re after a diamond that is not white, these are referred to as ‘fancy colour’ diamond, such as pink, yellow or cognac - which aren’t colour graded in the same way.



Clarity refers to the irregularities and marks that are present in most diamonds. These can appear as dark marks, specks and feather-like features. For a diamond that is clear to the naked eye, choose a VS2 or SI1. These aren’t the most flawless of diamonds, but choosing a stone with a higher clarity grade will drive up the cost of your diamond engagement ring.

You may prefer to choose a diamond where any inclusions are located near the edge of the diamond - where they can be covered by the claw of your engagement ring setting. Locating inclusions within a diamond can be difficult - they’re not always easy to spot - but our experts will always point out any flaws when you view diamonds in our studio.


Carat Weight

Diamond carat weight is a measurement of how much the stone weighs, a metric “carat” is defined as 200 milligrams, or one fifth of a gram. Whilst diamond carat weight significantly impacts the cost of a diamond, a high carat weight will be devalued by a poor cut, colour or clarity grade. For example, a stone with high carat weight, but poor cut may appear smaller or larger than an excellent cut stone, with a much duller appearance due to the poorly executed facets.

You may have an idea of the certain carat weight you’d like to hit, but don’t neglect the importance of cut and colour, which have a huge impact on the beauty of the stone. When you sacrifice a few carat points, the difference between size may even seem negligible - few could tell the visible difference between a 0.95ct and 1ct diamond - yet the price difference could be significant.


 Diamond Cost

Learn about diamond pricing

Graded by the GIA, each diamond we supply is priced depending on its independently graded characteristics. The indicative prices below are based on GIA grading standards.


Pricing based on a GIA Certified Round Brilliant, Excellent Cut, Polish, Symmetry with Nil Fluorescence. Available to view in London.


Diamond Shapes

Diamonds can be cut in to a range of shapes, usually chosen to best optimise the qualities of the rough diamond. Find the right shape to suit your taste, or get in touch to learn about other, unique shaped diamonds.

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 Diamond Certification

GIA Certified Diamonds

Independently assessed, GIA diamonds are graded to the strictest, highest standards, meaning the diamond you view will not have been graded too generously, and will always live up to its certified grades, or even exceed them. There are a number of laboratories across the globe that certify diamonds - most of them too generously, meaning buyers overpay for a diamond that isn’t worth the money. At Holts Gems, we only supply GIA certified diamonds, because we want to ensure each part of your diamond engagement ring is of the highest quality possible.


Responsibly Sourced

As a trusted Hatton Garden jewellers, we have both a responsibility and desire to source and sell ethical diamonds. In sourcing GIA certified diamonds from the most trusted and transparent suppliers, we’re confident in the ethical provenance of our diamonds. Alongside our strict policy to only deal with credited and transparent diamond suppliers, we wholeheartedly support the UN’s Kimberley Process, given it has now ensured that 99.8% of diamonds in the global market are conflict free.

We recognise that 99.8% is an admirable figure, but continue to support the trade of conflict-free diamonds and look forward to the day that 100% of diamonds in the global market are ethical diamonds.




Connect with our experts

Whether you’re ready to begin the process of finding the perfect diamond, or would like a little more info, we’re here to help. Book an appointment or get in touch to speak with one of our experts.


Learn more about diamonds


What are diamonds?

A solid form of carbon, diamonds occur when carbon atoms are arranged in diamond cubic crystal structure. Naturally, diamonds form for billions of years within the Earth’s mantle, the intense pressure and heat of which encourages the carbon atoms to crystalise and form diamonds as we know them. Whilst they are formed from pure carbon, some diamonds impurities which affect their appearance, such as the presence of nitrogen, which makes a diamond yellow in tone, or boron, which results in a blue diamond. 


Where are diamonds found?

The geography of where diamonds are found depends largely on the volcanic activity of an area. Naturally occurring diamonds are found within Kimberlite rocks, which are found along the trails of old volcanic pipes. Essentially, the diamonds, which form in the Earth’s mantle are thrown up to the Earth’s surface by volcanic eruptions. Often, diamonds are also found in alluvial deposits, which are the sediment deposits left behind by rivers and streams, as the rocks transported by the movement of the water.

Whilst diamonds are relatively rare gemstones, they can be found in a variety of locations across the globe, thanks to the presence of kimberlite. Diamonds are found in 35 different countries, most notably, South Africa, Russia and Botswana, but also areas around Canada, the US, China and Brazil. Diamonds are most often associated with South Africa, as this is where the 83.5ct Star of Africa, once the world’s largest diamond, was found in 1869, sparking the diamond rush of South Africa. Soon after, the diamond monopoly De Beers was founded in area.

Once mined, diamonds move to various hubs dedicated to such professions as diamond cutting and polishing and diamond grading. Located in the USA, the GIA are the most notable diamond grading lab, whilst cutting and polishing often takes place in India and Belgium. After these processes, the diamonds end up with various suppliers - many of the UK’s being based in Hatton Garden. This makes the business of crafting engagement rings in Hatton Garden all the more smooth, our close access to a diverse plethora of diamonds enabling our experts to handpick each stone with strict standards, ensuring our clients see only the finest and best diamonds for their specific preferences and budget. 


Are diamond engagement rings ethical?

Diamonds are loved and adored by many across the globe, but for sometime now, they have held negative connotations as drivers of war, conflict and rebellion in mining countries. Luckily, huge measures have been taken to eradicate the trade of conflict diamonds, which are now thought to account for as little as 0.2% of diamonds in the world’s trade. 

Holts Gems recognise the need to transform the jewellery industry, and are proud supporters of the UN’s resolution effort - the Kimberley Process. The Kimberley Process mandates that countries across the globe may not trade in rough diamonds sourced from any country considered to be using mining profits to fund civil war or violations of human rights. Thanks to the process, which requires origin certifications to prove traded rough diamonds are conflict free diamonds, ‘participants actively prevent 99.8% of the worldwide trade.’

As well as whole heartedly supporting the Kimberley Process, Holts Gems are committed to only using the most transparent and trusted diamond and gemstone suppliers, and specialise in sourcing GIA certified diamonds. 

If you’d like to further ensure you choose an ethical diamond for your engagement ring, you may want to consider a lab grown diamond. Still regarded as ‘real diamonds’, lab grown diamonds are structurally the same as mined diamonds, but with origins inside a lab, forgo uncertain ethical issues.


What diamond carat size should I buy?

Knowing what carat size to aim for for your engagement ring can be tricky. Some buyers like to know how much a one carat diamond costs, and then work from that - but the truth is, it’s difficult to put a guide price on diamonds. This is because the price of diamonds varies hugely depending on specific characteristics of each stone - most notably, the carat, cut grade, colour grade and clarity grade. You can learn more about how much diamond engagement rings cost here.

Essentially, the answer is to work back from your guideline budget, and make the most of the expertise of our diamond and gemstone experts - they’re here to help you figure out exactly what you’re after. Once you’ve got an idea of you budget, and have figured out the setting style you like, you’ll know how much you have left to spend on the diamond - which in turn will give you an idea of the carat size you’ll be looking at. 

You can learn more about how much engagement rings cost with our dedicated guide.