Diamond Cut Guide: Grades & How Diamonds Are Cut

The cut of a diamond creates that unforgettable sparkle we all look for when shopping for the perfect engagement ring. However many of our customers do not realise that an excellent cut diamond can appear larger than other diamonds of the same shape and carat weight. How? It's all down to the diamond's dimensions, angles and proportions. In this quick and simple guide, we will explain the differences you need to know between an  “Excellent cut”, “Very Good cut” and “Good cut ” diamond, when shopping for a diamond engagement ring.

Would you like to see the difference between each diamond before it is set into the ring setting? Our diamond specialists can help you compare loose diamonds side by side and talk you through the GIA certificate so that you can buy with confidence. Book an appointment in your local Diamond Heaven store or contact Diamond Heaven today for advice and guidance before buying. 

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WHAT IS A DIAMOND CUT? (AND HOW IT DIFFERS FROM SHAPE)

Diamonds do not emerge from the earth in the beautiful shapes we see in jewellery today such as round, oval, emerald, and pear, etc. They are first known as rough diamonds which then need to be cut into their desired shapes by a diamond cutter. Every rough diamond is unique and needs to be cut to the best of its ability into the right shape and proportions which maximise that diamond's carat weight, light performance and beauty. The deciding factors on what that diamond's shape and carat weight will be is guided by a diamond cutter's skill, craftsmanship and the clarity characteristics of that diamond. You will find that the higher graded diamonds such as an Excellent Cut have more brightness, fire and scintillation which creates more sparkle of white light and spectral colours when you move the diamond. 

 

WHY CUT MATTERS THE MOST FOR SPARKLE

Even with high grades in a diamond's colour and clarity, the diamond can still appear dull if its cut grade is a ‘poor cut’ or ‘Fair cut’ diamond as the diamond can be cut too deep or too shallow which stops the light from passing through the diamond and this affects the diamond's sparkle. 

Excellent-cut diamonds offer the best:

• Brightness (white sparkly light)

• Fire (flashes of spectral colours)

• Scintillation (the bright sparkle you see as the diamond moves)
  
  

With all of these factors combined, it’s no wonder that the cut quality is the single biggest driver of how sparkly a diamond looks, even at arm’s length.

 

WHAT ARE THE CUT, POLISH AND SYMMETRY DIAMOND GRADES?

All diamonds have a polish grade and symmetry grade however only round brilliant cut diamonds need all three grades as the third grade the ‘cut’ relies on the equilateral shaping of the round brilliant which is known to be the most sparkly of all the shapes. The GIA cut grade scale explains the grading for this and will still assess fancy shaped diamonds such as ovals, pears and emeralds which are not symmetrical with just the two grades.

What do these three grades mean:

• Symmetry (How well the diamond has been cut in terms of dimensions and proportions to be symmetrical)

• Polish (How well the diamond is then polished)

• Cut (The third grade given to only Round Brilliant cut diamonds to assess how even the rounded shape is)
  
  

 

HOW TO UNDERSTAND GIA'S DIAMOND CUT GRADING SYSTEM

The GIA grades for the polish, symmetry and cut are: Excellent, Very Good, Good, Fair, Poor. Most reputable jewellers will not stock or sell Fair and Poor cut diamonds, they are not as visually sparkly and can appear hazy, always check the diamond certificate to be sure you are buying a diamond at at least a Good cut and then assess the price difference to upgrade this to a very good cut or excellent cut depending on your budget. 

EXCELLENT

The best cut grade by GIA standards you can choose, this ensures the diamond is in perfect proportion to reflect and refract the light, usually these diamonds will look like a larger more impressive size from the top view as they are not cut too deep meaning you can see more of the carat weight from the top view which can make them appear larger than another diamond with the same or even a slightly higher carat weight! An Excellent cut (GIA recognised) or Ideal cut diamond (AGI & IGI recognised) will allow for optimum light, fire and sparkle. If you have movement in your budget, always consider this option.

VERY GOOD

Still considered a very desirable cut grade and second from the top! A very good cut allows nearly as much light to refract through the diamond as much as an excellent cut but at a considerably lower cost, a very good cut is a great choice to ensure a superior quality and stay within your budget.

GOOD

Diamonds graded as a Good cut reflect a satisfactory amount of light and sparkle. However it is not as noticeable at arms length. A Good Cut diamond is a great value for money, without having a dull appearance inside your diamond and you will still get a sparkle from your diamond in this range and it is a great choice if you are shopping on a strict budget and want to prioritise the cart weight. This cut is in the top 25% of diamonds on the market and seen in most high street stores where they will not explain the difference between this cut grade and higher grades as many will not stock all grades due to their cost and value.

FAIR / POOR

These are the lower cut grades which you will not see often on the market, however they do exist and that's why they are on the scale. These diamonds have uneven proportions and can be cut either too deep which creates a dullness to the diamond or too shallow which creates a dark shadow in the center of the diamond. This is caused from the light leaking out of the diamond which will reduce its sparkle and brilliance; the face view of the diamond will usually have a dull or glassy appearance. We don’t recommend these grades and this is why you will not see them offered on our website but it is important to know the difference when choosing the higher grades and why there is a price difference between each cut grade. You will only see a few of these on the market which are sold mainly in large carat weights, as they are a great price point for a customer that wants to prioritise the size of the diamond over the quality. We would not advise viewing any diamonds you are considering buying in these grades in person and comparing them to a smaller carat weight in one of the top three cut grades to see what is more important to you. 

 

DIAMOND CUT CHART

Every diamond is graded on its cut quality and is given a grade ranging from excellent to poor. The higher the cut grade, the better the fire and shine that is emitted from the diamond. Our diamond cut charts explain how each grade is assessed.

 

 

HOW ARE DIAMONDS CUT?

Diamonds are cut through a precise, staged process that balances light return with weight (carats):

1. Planning and mapping
The rough crystal is 3D-scanned to map inclusions and plan the best use of the rough diamond. Diamond cutters decide whether to maximise brilliance or retain carat weight and decide whether to create two smaller diamonds from one rough vs one larger diamond).

2.  Cleaving or laser sawing
The rough diamond is split or sawn (now typically with lasers) along natural grain lines or cleavage to create two diamonds from the rough.

3. Bruting (shaping the outline)
The pre-forms are rounded or shaped. For a round brilliant, the cutter “brutes” the diamond against another diamond or a lathe to create a perfect circular girdle; for fancy shapes (oval, pear, emerald, cushion), the outline is formed to a template.

4. Faceting – blocking then ‘brillianteering’
Cutting begins with “blocking” the main facets (table, eight crown mains, eight pavilion mains, plus culet if used). “Brillianteering” is the next stage where the final facets are added to reach the classic 57 or 58 facets for a round brilliant cut. The faceting process of creating angles, symmetry and alignment is what defines the diamond's brightness, fire and scintillation making this a very crucial part of the process which relies on the craftsmen’s level of skill to create the perfect diamond facets.

5. Polishing
Each facet on the diamond is polished on a fast-spinning diamond wheel called a ‘scaife’ using diamond powder. This High-quality diamond polishing powder removes microscopic lines and light abrasions on the diamond so light isn’t scattered or dulled and allows more light to shine through the stone.

6. Quality control and grading
The finished diamond is checked for proportions, symmetry and polish. Round brilliant cuts can receive the three GIA cut grades. Every decision, such as the size of the diamond table (the large center facet on the top of the diamond), how deep the pavilion (bottom half of diamond), the thickness of the girdle, and how the facets align, affects whether light returns to your eye or leaks away through the other sides of the pavillion of the diamond. That’s why the cut grade is one of the biggest considerations you need to make which will affect how much your diamond sparkles.

 

WHICH CUT SHOULD I CHOOSE?

At the end of the day always remember the right cut grade is the one that looks best to your eye and fits your budget. As a rule, Excellent to Very Good cuts deliver the most sparkle and are worth considering the price difference. They tend to offer a larger face up size appearance compared to lower cut graded diamonds in a similar carat weight. Avoid Fair and Poor cuts and if you are considering these grades check the diamond in person before making a purchase, compare them to higher graded diamonds to be sure what you think is best for you and make that decision yourself whilst comparing them in person to the naked eye.

Need more diamond advice? Book an appointment or speak to our team on 0345 222 5009 or [email protected].

 

HOW TO PRIORITISE BETWEEN CUT, CARAT WEIGHT, SIZE AND BUDGET

If you’re deciding between a slightly larger, lower-cut stone and a slightly smaller, higher-cut stone, remember that most people notice sparkle before size. A higher cut grade can make a diamond look brighter and more sparkly and often appear larger than a bigger but poorly cut alternative.

 

OUR PRACTICAL BUYING CHECKLIST

At Diamond Heaven, your appointment is private, relaxed and genuinely helpful. We give you an itemised quote with lifetime aftercare, so you can choose with confidence, not pressure.

When you view diamonds with us, we will:

• Compare the diamonds sparkle in different lighting settings

• Offer you a Jewellers loupe (x10 magnifier) to look at the diamond up close

• Walk you through the GIA report (cut, symmetry, polish, table, depth)

• Show how proportions affect the diamonds light performance

• Help you compare cut against carat weight, colour and clarity for your budget
  
  

 

FAQS ABOUT DIAMOND CUTS

Which diamond cut sparkles the most?

For maximum shine, the round brilliant (in a triple Excellent) shows the highest brightness and fire due to its facet pattern and symmetry. Fancy shapes can be very sparkly when graded Excellent on both the symmetry and Polish grades.

Does cut affect how big a diamond looks?

Yes. Excellent-cut diamonds often look larger from the top view and appear more vibrant than fair or poor cut diamonds of a similar carat weight because they return more light to the eye and they are not cut too deep or too shallow affect the proportions and angles needed to reflect and refract light.

Is “Ideal” the same as GIA Excellent?

“Ideal” is a trade term often used to describe diamonds with superior proportions and finishing; GIA’s Excellent grade is the most reputable and well known highest diamond cut laboratory grade. However other laboratories claim that the “ideal” graded diamonds would be graded to the equivalent of the GIA Excellent cut grade, but “ideal” itself isn’t a GIA term.

What is a diamond cut wedding ring?

A “diamond-cut” wedding ring usually refers to a metal wedding band engraved with tiny, faceted patterns; this is not related to a diamond, but a pattern in the metal similar to diamond faceting which catches the light beautifully. The effect adds sparkle-like flashes to plain gold or platinum bands and is a popular choice for a wedding ring pattern. 

What is diamond cut detailing on jewellery?

Diamond cut detailing refers to decorative shaping and micro-faceting metal on a piece of jewellery, these patterns are engraved into the metal surface (often by machine) to create crisp, reflective patterns similar to the faceted angles of a diamond. It’s a great way to add texture and light play to plain bands or little detailed accents.

What cut grade should I choose on a tighter budget?

Consider a Very Good or Good cut in a balanced carat/colour/clarity mix. In many cases, you’ll see more beauty from a higher cut grade and slightly lower colour/clarity than the reverse and consider the minimum carat weight you would accept ith this quality compared to a slightly larger but duller diamond.

How many facets does a round brilliant have?

A classic round brilliant has 57 or 58 facets (58 if the culet is present). Precision in facet alignment is key to symmetry and light return.

Do modern diamond cutters still cleave stones by hand?

Whilst traditional cleaving exists, most separation is now done with precision lasers, which create cleaner cut lines and minimise the risk of shattering along the grain.

What tools are used to cut and polish diamonds?

Cutters use laser saws for splitting, bruting lathes, (or diamond-on-diamond) for shaping, and rotating scaifes with diamond powder to polish each facet to perfect precision.

How long does it take to cut and polish a diamond?

It varies by size and shape. A small round brilliant can take days; larger or more complex fancy shapes can take weeks due to extra planning and fine polishing.

Can my diamond be re-cut to improve sparkle?

Yes, this is possible. Re-cutting a diamond can enhance brilliance and symmetry, but it removes carat weight and potentially the diamond's value, as the first time they are cut it is to maximise that diamonds highest value potential, changing the carat weight can lower the value and affect the current certification, meaning it will need to be sent off to be graded again. Always seek professional advice first before considering this diamond as many jewellers offer to upgrade your diamond instead of this option.

How do I check cut quality in a showroom?

You can view stones under different lights, compare side-by-side, and review the grading report for the diamonds cut, symmetry and polish. We do all of this with you at Diamond Heaven as we sell loose diamonds and allow you to assess which one you prefer as a loose diamond before setting it into your chosen ring design so that you can see every angle of the stone before committing to a purchase. Contact us here.