The Seven Steps to Buying the Best Diamond

Most people will have heard of the 4 C’s of diamonds. These are carat, cut, colour and clarity. However, whilst these may be the four most important aspects of diamond buying, there is actually more to consider. If you are looking to purchase loose diamonds or diamond jewellery such as an engagement ring from Commins & Co. There are seven main things you should take into consideration to ensure you get the best diamond possible. This guide will take you through the seven steps. We explain why they are so important helping you to get the best diamond for your money.

The Seven Steps to Buying the Best Diamond

1. Choose your cut quality
2. Select your carat weight
3. Choose your preferred colour grade
4. Consider the optimal clarity grade
5. Take into consideration polish, fluorescence and symmetry
6. Choose the diamond shape
7. Choose the right certificate

1. Choose your Cut Quality

The cut of a diamond is one of its most defining features. The cut quality of a diamond will have a notable effect on its price. Determining its proportions and how it reflects light. The cut of a diamond is graded with the higher grades being more desirable than lower grades. Diamond cutA diamond’s cut could be graded as;

Super ideal, Only 5% of diamonds will be graded as super ideal and their rarity makes them more valuable.

Ideal / Excellent will have superior craftsmanship, these diamonds emit the most light and brilliance.

Very good, good, and fair. These diamonds are an economical choice for buyers. If possible, try to buy a diamond graded as at least ‘good’. This will allow the diamond to sparkle.

2. Carat Weight

The single most important factor that influences the price of a diamond is its carat weight. The higher the carat weight, the larger the diamond. It is also important to consider the cut with the carat weight. A poorly cut diamond can look smaller than an excellent cut diamond of smaller carat weight. When considering the carat value of a diamond, many people believe it refers to the size of the diamond. It actually refers to its weight.

3. Choose your Preferred Colour Grade

The colour of a diamond can have a serious effect on its appearance and value. Diamond colourDiamonds are available in a variety of colours, with pink or blue being extremely rare pieces. With a white diamond, however, any hint of yellow will reduce the light reflected from it. Any yellow tint to a white diamond is undesirable. The colour of a diamond is graded from D – Z with those graded D having next to no colour both under magnification and to the naked eye. At the other end of the scale, those graded as S-Z will have a noticeable brown or yellow tint, making them much less desirable.

4. Consider the Optimal Clarity Grade

In diamonds, clarity refers to the absence of any blemishes or inclusions.Diamond clarity As diamonds are naturally created from carbon with deep pressure and tremendous heat. As a result blemishes can occur on the surface. Also, internal marks known as inclusions may be present. Diamond clarity is graded from flawless which have no inclusions or blemishes  visible through to included.

In Ireland, diamonds with the clarity grade of SI1 or SI2 are the most commonly purchased diamonds. It is important to note that the quality of an SI2 varies from diamond to diamond. Some SI2’s are eye clean, with others having visible blemishes. At Commins & Co Jewellers, our experts hand pick the best SI2’s. This is through our network of diamond suppliers making sure they are the eye clean diamonds our customers look for.

5. Polish, Fluorescence and Symmetry.

The polish, fluorescence and symmetry of a diamond will all affect its value. Polish refers to how smooth the surface of a diamond is. A higher grade can be achieved by using a finer grain on the polishing wheel. In reality, it can be difficult to distinguish the differences. These range between an ‘excellent’, ‘very good’, or even ‘good’ graded polished diamond.

Fluorescence refers to how the diamond responds under ultra-violet light. Those with strong blue fluorescence are more likely to be slightly hazy under normal lighting.

The symmetry of a diamond refers to the degree of alignment of the facets of the diamond. For most buyers, diamonds with symmetry that is graded as ‘excellent’ and ‘good’ will exhibit virtually no difference. Symmetrical defects are usually only noticeable in diamonds rated ‘fair’ or ‘poor’.

6. Choose the Diamond Shape

Choosing the diamond shape is mainly a matter of aesthetics. However, the cut of a diamond can affect its value. Round brilliant round cut diamonds being more valuable than ‘fancy-shaped’ diamonds. The shape of a diamond can influence its quality, cost and overall appeal.

The round cut is the most popular diamond shape, giving the maximum reflection of light. Other popular cuts include oval, radiant and emerald.

7. Choose the Right Certificate

Diamonds are evaluated and certified by independent labs. They are scrutinised and evaluated by trained professionals using professional tools. The most common certification labs are the  GIA, HRD and IGI. Each lab may grade and describe diamonds slightly differently. Ensuring you purchase certified diamonds from a reputable certification lab is important. This ensures the quality of what you are buying.

Purchasing a certified diamond engagement ring or loose diamonds from Commins and Co gives you peace of mind that the diamond has been examined in detail by a gemologist and is accompanied by an independent certificate. The examination is unbiased and ensures you are getting what you are paying for. Diamonds that are sold without certification may be graded higher than they actually are. As a result, you are paying more money for a lower quality gem.

Commins & Co diamonds are certified by either:
(i) GIA – The Gem Institute of America which is widely renowned as the most respected and prestigious laboratory in gemmology,
(ii) IGI – the International Gemological Institute,
(iii) HRD Institute of Gemmology, Antwerp.


Some of the steps involved in purchasing diamonds will have more effect on their value than others. If you start with the 4 C’s with carat, colour, clarity and cut as the highest level of importance. Then take into account the other factors that can influence the appearance, desirability and value of a diamond. You should be able to select the perfect gem to suit your engagement ring requirements and budget.

At Commins & Co Jewellers we have over five hundred engagement rings ready to view in store. One of our Brilliant Cut Solitaire diamond engagement ring is a good example of how to follow the seven steps. This ensures you get value for your money. This is but one of many examples. For further information and assistance please contact our award winning team now!