The Complete Diamond Buying Guide: Everything You Need to Know Before You Buy
By Amr Ramadan DGA, Hatton Garden Jeweller & Founder of Mouza Fine Jewellery
The diamond buying process has changed dramatically since I started in this industry.
When I began my training at Gem A London over ten years ago, most people bought diamonds by visiting local jewellers, relying heavily on personal recommendations and face-to-face guidance.
Today, buyers arrive armed with spreadsheets, online research, and detailed knowledge of the 4Cs yet many are more confused than ever. This paradox reflects a fundamental shift in how people approach diamond purchasing. Information is more accessible than ever, but the sheer volume of choices and conflicting advice can be overwhelming.
The rise of lab grown diamond rings has added another layer of complexity, while online retailers have changed pricing transparency and shopping expectations.
After working my way through major Hatton Garden showrooms as a gemologist and sales manager, and now running Mouza Fine Jewellery, I’ve observed that successful diamond buying isn’t about memorising technical specifications or finding the “perfect” stone on paper.
It’s about understanding what creates beauty, knowing where to prioritise your budget, and making informed trade-offs that align with your values and preferences.
The modern diamond market offers unprecedented choice and value, but it also requires more sophisticated decision-making. Whether you’re considering natural diamonds with their geological heritage or exploring lab-grown alternatives with their modern precision, the principles of smart buying remain consistent.
The goal isn’t to become a gemologist overnight it’s to understand enough about diamonds to make confident decisions that you’ll be happy with for decades to come.
Before You Start: Setting Realistic Expectations
Understanding Your Budget
Here’s the first thing I tell every customer: decide on your budget before you start looking at diamonds, not after.
I’ve seen too many people fall in love with a diamond that’s twice their budget, then spend months trying to justify the extra expense or feeling disappointed with what they can actually afford.
Your budget should be what you can comfortably afford without going into debt or compromising other financial goals.
The old “two months’ salary” rule is marketing nonsense from the 1930s. Spend what makes sense for your situation.
Once you have your budget, stick to it. A good Hatton Garden jeweller will work within your parameters and show you the best options available, not try to push you beyond what you’ve said you can spend.
The 4Cs: Important, But Not Everything
Everyone talks about the 4Cs cut, colour, clarity, and carat weight and they are important.
But they’re just the starting point. I’ve seen people get so focused on achieving certain grades that they forget to consider
whether the diamond is actually beautiful. The 4Cs tell you what a diamond is on paper. But beauty, brilliance, and how the stone looks on someone’s hand that’s something you need to see for yourself.
Step 1: Choose Your Shape First
This might seem backwards, but I always recommend choosing your diamond shape before you worry about the 4Cs.
Why? Because different shapes have different strengths, weaknesses, and ideal proportions. What makes a round brilliant beautiful isn’t the same as what makes an emerald cut stunning.
The Shape Affects Everything Else
Round brilliants are the most brilliant but also the most expensive.
Fancy shapes like ovals, cushions, and emerald cuts can give you more size for your money, but they each have their own considerations.
Emerald cuts show colour and clarity more readily, so you might need higher grades. Ovals and cushions can have bowtie effects that you need to watch for.
Don’t just look at pictures online. If possible, see different shapes in person or 360 videos.
I’ve had countless clients change their minds completely once they see how different shapes look on an actual hand.
Step 2: Understand Cut Quality (The Most Important C)
If I could only give you one piece of advice about buying diamonds, it would be this: prioritise cut quality above everything else.
A well-cut diamond will always look more beautiful than a poorly cut one, regardless of the other Cs.
What Cut Quality Really Means
Cut isn’t just about the shape it’s about how well the diamond has been faceted to interact with light.
A well-cut diamond captures light, bounces it around inside, and sends it back to your eye as brilliance and fire.
A poorly cut diamond lets light leak out the sides and bottom, leaving you with a dull stone.
For round brilliants, look for GIA Excellent or IGI Ideal cut grades.
For fancy shapes, it’s more complicated because GIA doesn’t assign cut grades to non-round diamonds. This is where working with a knowledgeable Hatton Garden jeweller becomes crucial.
The Numbers That Matter
For round brilliants, here are the proportions that create the best light performance:
Table percentage: 54-59%
Depth percentage: 58-62%
Crown angle: 34-35 degrees
Pavilion angle: 40.6-41 degrees
These aren’t just random numbers they’re the result of decades of research into diamond optics.
Diamonds cut within these ranges will consistently show excellent light performance.
Step 3: Colour – Where You Can Save Money
Diamond colour is graded from D (completely colourless) to Z (light yellow or brown).
Here’s what most people don’t realise: unless you’re comparing diamonds side by side, it’s very difficult to see the difference between adjacent colour grades.
The Sweet Spot for Value
In my experience, the best value in diamond colour falls in the G-J range.
These diamonds appear colourless to the naked eye but cost significantly less than D-F colour stones.
The setting metal also affects how colour appears. If you’re choosing a 18k yellow gold setting, you can easily go down to J or even K colour without any noticeable difference. With platinum or 18k white gold, I usually recommend staying in the G-I range.
When Colour Matters More
Emerald cuts and Asscher cuts show colour more readily than brilliant cuts, so you might want to go up a grade or two.
Large diamonds (over 2 carats) also show colour more easily, so higher colour grades become more important as size increases.
Step 4: Clarity – What You Can and Can’t See
Clarity measures the presence of inclusions (internal flaws) and blemishes (surface flaws). The scale runs from Flawless (FL) to Included (I3), but here’s the secret: most inclusions that affect the clarity grade are invisible to the naked eye.
The Eye-Clean Standard
What you want is an “eye-clean” diamond one where you can’t see any inclusions without magnification.
Depending on the size and shape of your diamond, you can often find eye-clean stones in the VS2 or SI1 range.
I regularly show clients SI1 diamonds that they swear look flawless. To the naked eye, they are flawless, and that’s what matters for daily wear.
When to Go Higher in Clarity
If you’re buying a large diamond (over 2 carats) or a step-cut shape like emerald or Asscher, you might need higher clarity grades. These cuts and sizes make inclusions more visible.
Also, if you’re planning to upgrade your diamond in the future, higher clarity grades hold their value better.
Step 5: Carat Weight – Size vs Quality
Carat weight is probably the most misunderstood of the 4Cs.
People think it’s about size, but it’s actually about weight. A well-cut diamond can appear larger than a poorly cut diamond of the same carat weight.
The Magic Numbers
Diamond prices jump at certain carat weights 0.50, 0.75, 1.00, 1.50, 2.00, etc. You can save significant money by staying just under these thresholds.
A 0.95-carat diamond costs much less than a 1.00-carat diamond but looks virtually identical.
Making Your Diamond Look Larger
The engagement ring setting can make a huge difference in how large your diamond appears.
Halo ring settings (small diamonds surrounding the centre stone) can make a diamond look significantly larger. Dainry bands make the centre stone appear bigger by comparison.
The shape also affects apparent size.
Elongated shapes like elongated cushion, marquise, and emerald cuts often appear larger than round diamonds of the same carat weight because they have more surface area.
Step 6: Certification – Why It Matters
Always, always, always insist on proper certification. For diamond engagement rings, that means GIA or IGI certification. These are the only two labs I trust for accurate, consistent grading.
Why Other Certifications Fall Short
I’ve seen diamonds graded by other labs that were off by 2-3 grades compared to GIA standards. A diamond sold as “G colour, VS1 clarity” by a lesser lab might actually be “J colour, SI2 clarity” by GIA standards. That’s a huge difference in value.
What to Look For
The certification should match the diamond exactly.
Most GIA diamonds have a microscopic laser inscription on the girdle that matches the report number.
This ensures you’re getting the exact diamond described in the report.
Step 7: Setting Your Budget Priorities
Once you understand the 4Cs, you need to decide which factors matter most to you. Here’s how I usually guide clients through this decision:
If Brilliance Is Your Priority
Focus on cut quality first, then colour, then clarity, then carat weight.
A smaller, well-cut diamond will always look more impressive than a larger, poorly cut one.
If Size Is Your Priority
Consider fancy shapes, which typically cost less than rounds.
Look at the lower end of the colour and clarity ranges where you can still get eye-clean, near-colourless stones.
Consider lab-grown diamonds, which can give you significantly more size for your budget.
If Investment Value Matters
Stick with round brilliants, higher colour and clarity grades, and natural diamonds. These hold their value best over time.
Where to Buy: Online vs In-Person
The Online Advantage
Online retailers often have better prices because of lower overhead costs.
They also have larger inventories, so you’re more likely to find exactly what you’re looking for.
Many now offer high-quality images and 360 videos that let you see the diamond in detail.
The In-Person Advantage
There’s no substitute for seeing a diamond in person.
You can judge the cut quality, see how it performs in different lighting, and get a sense of how it will look when worn.
A knowledgeable jeweller in Hatton Garden can also guide you through the selection process and help you understand what you’re looking at.
Hatton Garden: The Best of Both Worlds
Shopping in Hatton Garden gives you access to some of the world’s most experienced diamond dealers with competitive pricing.
At Mouza We see thousands of diamonds, so we can quickly identify the best stones and guide you away from poor performers.
The best Hatton Garden jewellers combine expertise with competitive pricing.
We’re not just selling you a diamond we’re sharing decades of experience to help you make the best choice.
Frequently Asked Questions
How much should I spend on an engagement ring?
Spend what you can comfortably afford without going into debt. The old “two months’ salary” rule is outdated marketing.
Your budget should reflect your financial situation and priorities.
Are lab-grown diamonds real diamonds?
Yes, lab-grown diamonds are real diamonds. They have the same chemical, physical, and optical properties as natural diamonds. The only difference is their origin.
What’s the best diamond shape?
There’s no “best” shape – it’s entirely personal preference. Round brilliants are the most popular and brilliant, but fancy shapes can offer better value and unique character.
How can I tell if a diamond is well-cut?
For round brilliants, look for GIA Excellent or IGI Ideal cut grades. For fancy shapes, you need to rely on proportions and visual inspection, which is where an experienced jeweller’s guidance becomes valuable.
Should I buy online or in person?
Both have advantages. Online often offers better prices and selection, while in-person allows you to see the diamond and get expert guidance.
Many people research online and buy in person, or vice versa.
What if I’m not happy with my purchase?
Reputable dealers offer return periods, typically 7-30 days. Make sure you understand the return policy before purchasing, and inspect your ring carefully upon delivery.
How often should I have my diamond ring checked?
Every 6-12 months for a basic inspection to ensure prongs are tight and the diamond is secure. More frequently if you’re very active or work with your hands.
Can I upgrade my diamond later?
Many jewellers offer upgrade policies, but terms vary. Some require you to spend at least double your original purchase price. Understand the upgrade policy before buying if this is important to you.
The Path Forward: Making Confident Decisions
The diamond industry will continue to evolve.
New technologies will emerge, market dynamics will shift, and consumer preferences will change.
But the fundamental principles of smart diamond buying understanding quality, knowing your priorities, and working with trustworthy sources will remain constant.
After years of working with both natural and lab grown diamond rings, I’ve learned that the most satisfied customers are those who approach the buying process as an education rather than a transaction.
They take time to understand their options, ask thoughtful questions, and make decisions based on knowledge rather than impulse.
The best Hatton Garden jewellers understand this approach. We’re not just selling diamonds we’re providing guidance, education, and long-term relationships. The goal isn’t to make a quick sale but to help you find something you’ll treasure for decades.
The diamond market offers more choices today than ever before. This abundance can feel overwhelming, but it also means there’s a perfect diamond out there for every budget, preference, and value system. The key is approaching the search with patience, knowledge, and clear priorities.
Your diamond buying journey is unique to you. Whether you choose a classic round brilliant or an unusual fancy shape, whether you prioritise size or quality, whether you select natural or lab-grown the right choice is the one that aligns with your values and brings you joy.
Take your time, ask questions, and trust the process. The perfect diamond for your situation is waiting to be discovered.
