Diamond Buying Guide – The 4 C’s & More!

Buying a Diamond can be a daunting process as they are in many cases a very significant purchase, especially if it is for an engagement ring and you can easily end up feeling confused and overwhelmed by all the information and options available to you.

I know this from personal experience as I’ve been there myself but since I was in your position, I have become a fully qualified gemologist and ran my own online jewelry retailer.

So I do know a bit about Diamonds and that is why I created this in-depth guide to not only help you buy the perfect Diamond but also learn more about these awesome gems, so let’s get started…

Step 1: Set Yourself a Budget

I honestly can’t stress this one enough as setting a budget makes the whole process so much easier and as most Diamonds are bought to go into a piece of jewelry, such as an engagement ring, your total budget should cover:

  • The Diamond
  • The Mount (the piece of jewelry in which the stone is going to be set)
  • The cost of setting the Diamond and finishing the mount

And if you are buying through a retail store or directly from a jeweler, it doesn’t matter whether your budget is $500, $5,000 or £500,000, make sure to let the person you are buying from know.

This helps them tailor the piece to your budget, which makes the process much more enjoyable for you and a lot easier for them.

Because the problem with going in and saying something like “I don’t really have a budget” means that they have to do some detective work to find out how much you have to spend (because everyone has a budget!) as Diamonds can range from less than $1000 a carat to over $1 million a carat.

Step 2: Lab-Grown vs Mined Diamond?

It’s crazy as 10 years ago this wouldn’t even be a consideration but now one of the biggest choices when it comes to buying a Diamond is should you go for a lab-grown or mined Diamond?

The problem is that there isn’t a straightforward answer as it very much comes down to your own personal beliefs and preferences as to which one you choose but I would recommend doing research into this, preferably from independent sources such as my Lab-Grown vs Mined Diamonds post that takes a deeper look into:

  • The environmental & sustainability claims
  • The socio-economic impact of where the diamonds come from

This is because there is a lot of misinformation out there, along with a lot of unverified claims, especially around lab-grown diamonds in the marketing material that the manufacturers and retailers use.

When it comes to making this decision, there are a number of factors to consider, including:

  • Ethical preferences, which includes the two things I mentioned above
  • Purchase price and future potential value
  • Whether you want a Diamond that was created by nature or one that is man-made

The last thing I will cover in this section is that it can be useful to learn the different terminology that is used around these two types of Diamonds as it can be confusing when you are looking to buy one:

  • Lab-grown Diamonds
    • Laboratory grown Diamonds
    • Synthetic Diamonds
    • Man-made Diamonds
  • Natural Diamonds
    • Earth mined Diamonds
    • Mined Diamonds

Step 3: Choose a Style of Cut

The next step is to choose the style of cut that you want for your diamond and once again this will be down to personal choice.

The most popular cut for diamonds is the Round Brilliant but there are quite a few different styles of cut to choose from and the majority fall into one of two categories, which are brilliant and step cuts.

Round Brilliant Cut Diamond

Brilliant Cuts

As I said above, the Round Brilliant is the most popular style of cut for a Diamond but there are other shapes that have benefitted from the many years of research that many Diamond cutters have put into perfecting the Round Brilliant so that it produces the perfect amount of sparkle.

Variations of the Round Brilliant include the Oval, Pear, Princess and Radiant and if you are looking to buy a Diamond that really sparkles, then you want to go for a Brilliant Cut Diamond.

Oval Cut

Oval Cut

Pear Cut

Pear Cut

Princess Cut Diamond

Princess Cut

Radiant Cut

Radiant Cut

Step Cuts

The step cut is another popular style of cut but these generally don’t have the same levels of sparkle as that of the brilliant cuts due to the way the Diamonds facets are cut but the benefit of this is that step cuts usually have very few inclusions as they can’t be hidden as easily as they can with brilliant cuts.

The most popular styles of the step cut are the Emerald, Baguette and Asscher.

Emerald Cut

Baguette Cut

Baguette Cut

Asscher Cut

Asscher Cut

When it comes to choosing a style of cut, more popular styles will have a higher price per carat than a less desirable cut. For example, a 1ct G/VS Round Brilliant will have a higher price per carat than a 1ct G/VS Heart Cut.

Step 4: Diamond Quality

The next step is arguably the most daunting step, which is choosing the quality of the Diamond as there are a number of different things to consider and having an understanding of all of these does make the buying process a lot easier.

Now I’m not saying you need to become an expert but knowing all the terminology and what affects the price of Diamonds is important and stops you from just being sold to and I’m going to cover all of these below.

P.S. I’ll also add links to posts where I cover all of these things in much more detail if you want to learn more about them.

The 4 C’s

We have to start with the 4 C’s as these are the four main criteria that are used to assess the quality of a Diamond and as a result, have a big impact on the value.


The first of these is color, which is the body color of the stone and Diamond color falls into two main categories:

  • Colorless Diamonds – these make up the majority of Diamonds that are mined and sold (around 98% of all mined Diamonds)
  • Fancy Color Diamonds – these make up the remaining 2% and include all the different colors that are found in Diamonds, including Blue, Pink, Yellow and Red

For this post, I’m going to be focusing on the Colorless Diamonds as these are the most commonly bought, especially for engagement rings.

Somewhat confusingly, not all colorless Diamonds are actually colorless and the majority of Natural Diamonds have some level of tint, which is commonly yellow but can also be brown and sometimes grey.

Colorless Diamonds are most commonly graded against the GIA color grading scale, which goes from D to Z and can be seen in the image below:

When it comes to buying a Diamond, stones with higher color grades will attract a premium over ones with lower color grades but there are a few things to be aware of when it comes to color in Diamond:

  • All color is graded by looking through the pavilion of the Diamond, not the top
  • D-F color Diamonds are all completely colorless and the main difference is how ‘bright’ the Diamond looks
  • G and H color Diamonds are both colorless when looking through the top of the Diamond
  • Any hint of a tint only starts to become noticeable through the table at an I-color
  • M-Z Diamonds are often referred to as tinted and are actually quite difficult to buy

For the majority of people a F, G or H color Diamond will be ideal as they are colorless when viewed from the top, which is how they will be viewed when they are mounted.

The only reason why people go for a D color Diamond is because they can easily afford it and/or they want to brag that they have a D color Diamond.


The second of the 4 C’s is clarity and this is quite an important one as this is how free from inclusions the diamond is (which some people refer to as how ‘clean’ the stone is.

Once again, it is the GIA clarity grading scale that is the most popular and as can be seen in the image below, it ranges from Flawless to Included:

Many people almost obsess over clarity and always try to buy a Diamond with the highest clarity possible as they don’t want any imperfections in their Diamond but there are some things you need to know about clarity:

  1. Clarity is graded using 10x magnification, such as a loupe of microscope
  2. Inclusions that are visible to the naked eye will only be found in SI or I clarity Diamonds and this doesn’t apply to all SI clarity Diamonds
  3. Inclusions are much less noticeable in brilliant cut Diamonds, especially if they are under the crown facets
  4. It takes an experienced Diamond grader to tell the difference between Flawless, Internally Flawless, VVS and VS clarity Diamonds

For the majority of Diamond buyers, a VS clarity or nice SI1 will be ideal as the inclusions won’t be visible to the naked eye and no-one other than a trained Diamond grader with a 10x Loupe will be able to tell whether or not the stone has any inclusions.

Another thing is that having higher clarity doesn’t automatically mean that the Diamond will look better as I’ve seen VVS and VS clarity Diamonds that don’t look great and SI clarity Diamonds that look amazing.

I do recommend avoiding I clarity Diamonds as not only are the inclusions likely to be visible to the naked eye, meaning they don’t look great but some inclusions can also impact the durability of the Diamond.


The next of the 4 C’s is cut, which in my opinion is the most important of the 4 C’s as this has the biggest impact on how the stone looks.

Just to clear up any confusion, when talking about Cut in relation to Diamonds, we are talking about the quality of cut, not the shape of the cut that I covered above.

But why is cut so important? Well, how well the stone is cut determines how much brilliance and fire (also called life and sparkle) there is in the Diamond.

This can sometimes result in a Diamond with great color and clarity looking dull and lifeless due to being cut poorly.

When it comes to the quality of the cut, they are assessed on three factors:

  • Proportions (called Cut Quality on most reports)
  • Symmetry
  • Polish

The Proportions have the biggest impact on the look of the stone but good symmetry is also important.

Currently, only Round Brilliants cuts are graded one their cut, with each quality factor being graded from Excellent to Poor and Diamonds graded excellent in all three are often referred to as Triple X Diamonds.

A good cut grade does indicate that a Diamond will look good in person but it isn’t a guarantee due to the many factors that are involved in Cut grading.


The final one of the 4 C’s and by far the easiest one to understand is Carat as this is the unit of measurement that is used to weigh a Diamond and 1 carat is the equivalent of 0.2 grams.

The weight of a Diamond does have a big impact on the value of a Diamond as when all other factors are the same, a larger Diamond will be worth more than a smaller one.

An important thing to be aware of when it comes to weight is that there are certain thresholds that have a big impact on the value of a Diamond as they are more desirable and easier to sell, for example:

  • Based on all other factors being the same, a 1.01 carat diamond will have a much higher price per carat than a 0.97 carat diamond

But the crazy thing is that there will be no noticeable difference in the size of the Diamond, meaning you can buy a Diamond that looks the same but for a lower price per carat but this will affect any potential resale value further down the line due to the reasons mentioned above.

Other Diamond Quality Factors

While the 4 C’s are the main quality factors that are used to assess a Diamond, they aren’t the only ones that need to be considered that can impact the price of a Diamond and also the looks.


Probably one of the most misunderstood aspects of Diamond quality is fluorescence.

This is because many people in the industry wrongly think that having any fluorescence in a Diamond is a bad thing and should be avoided but the truth is that in the majority of Diamonds, fluorescence doesn’t have any impact on the look of the stone.

The only time it is a bad thing is when it gives the stone a milky appearance because this obviously impacts on the look of the stone but this is generally only found in Diamonds that have a very strong fluorescence but not every Diamond with very strong fluorescence will have a milky appearance.

Fluorescence is only seen when the Diamond is exposed to ultra-violet light but it can make some Diamonds really pop in sunlight.

All GIA Diamond Reports will include how much fluorescence the Diamond has and it can range from None to Very Strong and in terms of value, Diamonds with strong or very strong fluorescence will usually cost less per carat than the equivalent Diamond with no or faint fluorescence.

diamond fluorescence


Another quality factor to consider when buying a Diamond (and one I rarely see talked about) is whether or not the stone has been treated as this has a big impact on the value of a Diamond.

There are a number of ways that a Diamond can be treated and below I will cover the most common ones and the reason why they are done.

Clarity Treatments

Some Diamonds are treated in ways that reduce the appearance of inclusions, this doesn’t improve their clarity, it just makes some inclusions less obvious and there are two main clarity treatments:

  1. Laser Drilling – this is where they use a laser to drill down to a dark inclusion/s and then either burn away or bleach the inclusion so that it is not as obvious
  2. Fracture Filling – this is where they fill surface-reaching fracture/s with a high lead content glass to reduce their appearance, this can sometimes be done after a stone has been laser drilled

While they can make a Diamond look better, I recommend avoiding clarity treated Diamonds as laser drilling actually adds additional inclusions and fracture filling isn’t permanent as exposure to heat can remove the glass from the stone (fracture-filled stones also won’t be clarity-graded by the GIA).

Color Treatments

Something that is becoming more popular is color-treating diamonds and there are two main outcomes that they aim to achieve:

  1. Improving the color of the stone – some natural brown diamonds can be HPHT treated (high pressure, high temperature, which mimics what happens in nature) to make them colorless
  2. Change the color – there are many fancy color diamonds that have been treated to produce the color in the stone and these are usually significantly cheaper than naturally colored diamonds

I would always recommend buying a Diamond that hasn’t been treated but color-treated stones can be bought for a lot less than untreated ones. This does make them attractive as long as you are happy with having a color-treated Diamond and know that they will have very little resale value.

Diamond Reports

GIA Lab Report

Another factor to consider when buying a Diamond is whether it comes with a report or not and who issued the report.

Just for clarity (no pun intended), many retailers refer to reports as certificates with them often advertising Certified Diamonds even though this technically isn’t the correct terminology!

The GIA is the largest and most well-respected gem lab that produces Diamond reports and a stone accompanied by a GIA report will be worth more than the same quality stone with a report from another lab, such as AGS (now part of the GIA) or IGI or if it doesn’t have a report.

I do recommend buying a Diamond with a report and most major retailers only offer these anyway as you have a better idea of the quality of the Diamond you are buying, especially as reports now include information as to whether the Diamond is natural or lab-grown.

If you ever see a Diamond being sold with a certificate of authenticity, run away as fast as you can as no reputable gem labs issue certificates, only reports.

Step 5: Buy From a Reputable Source

The final step in the buying process is choosing where to buy your Diamond from and the options depend on if you are just looking to buy a Diamond or if you are looking to have a piece made.

Just Buying A Diamond

If you are just looking to buy a Diamond, then there are some great online options such as Blue Nile or James Allen that offer a huge range of loose Diamonds at very competitive prices and also offer very good customer service, which allows you to return your Diamond if you aren’t happy with it.

Buying a Piece of Jewelry or Engagement Ring

If you are looking to buy your Diamond and have it put into a piece of jewelry, then there are a few more options available, this includes:

  • Online Diamond Dealers, such as Blue Nile or James Allen that also offer a ring/jewelry making service
  • Independent designer-makers
  • Independent jewelry consultants
  • Independent retailers, these can be online or have a retail outlet
  • Large jewelry chains

If you know the style of Diamond and ring you want to buy, then I think some of the online retailers can be a really good option.

If you are looking to a more personalized experience and potentially having a more bespoke piece made, then going for an independent business is an option definitely worth considering.

I generally wouldn’t buy a Diamond from a large jewelry chain store as you are usually buying a piece that has already been made and the Diamonds set and while not always the case, the Diamonds that they sell are usually not the best quality.

When doing research as to where to buy your Diamond, there are some things you can consider, including:

  1. Word of mouth – nothing is better than getting a recommendation from someone who has dealt with them before
  2. Reviews – pretty much every business will have some reviews online, these may be on Google, Facebook or an independent review site
  3. Trade organizations – many organizations will have a list of members but I would always look for reviews for any that you are interested in

My final piece of advice is to go with your gut, if you go somewhere and something doesn’t feel right then walk away and find someone you feel happy dealing with.


I know that was a lot of information but my aim with the post was to give you all the information you need to buy your perfect Diamond.

When it comes to the quality of Diamond, for Mined Diamonds, I recommend:

  • Color – F, G or H
  • Clarity – VS1, VS2 or SI1
  • Cut – Very Good or Excellent
  • Carat – what you can afford

This should get you a really nice-looking Diamond without breaking the bank, unless you can afford it, then go for a D Flawless!

When it comes to actually buying your Diamond, you should be treated in a similar way you would (or should!) any other major purchase, especially for an engagement ring by:

  • Having a clear budget
  • Having an idea of what you want to buy before you go looking
  • Finding the right place to buy from

Then you shouldn’t go far wrong and will hopefully end up with the perfect Diamond, whether for yourself or that special person in your life.

I'm Paul Haywood FGA DGA, the owner and founder of Haywoods Gems, I'm a fully qualified Gemmologist and Diamond Grader from the Gemmological Association of Great Britain.

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