The Diamond Buying Guide – The 4Cs of Diamonds

Finding the perfect diamond goes beyond grade or the price tag. Each naturally formed diamond is different and has a number of factors contributing to its beauty. These are commonly known as the 4Cs of diamonds and understanding what each of these bring to the stone can help you choose your ideal diamond.

Every diamond is unique, and in addition to a diamonds 4 C's, personal taste also plays a big role in choosing the perfect diamond. This is especially important if you’re looking at diamond engagement rings. The sheer variety of diamonds available, coupled with as many ring styles can make the selection process overwhelming.

So how do you choose a diamond?

  • Have a basic understanding of the 4 Cs of diamonds

  • Understand the different cuts and colours available

  • Understand the style of ring you are wanting to set the diamond in

The four C’s of a diamond refer to the cut, carat, colour and clarity. The cut refers to the way the diamond is shaped. The carat is the weight of the gem. The clarity is the amount of flaws or inclusions. The colour refers to any tinting or shade of yellow present in the diamond.


The Four Cs: The Quality of A Diamond

Diamond Cut

The way a diamond is cut makes a big difference to its appeal. Cutting a stone to the right proportions, keeping its symmetry intact and giving it a beautiful polish at the end is done to maximise its dispersion of light and its brilliance. The cut for each diamond is made by extremely skilled craftsmen (known as diamond cutters) who use their expertise to study each individual stone before determining the right cut for it.

The cut grade of a diamond ranges from ‘Excellent’ to ‘Poor’. At Diamonds on Richmond, Auckland we only sell ‘Excellent’ or ‘Very good’ cut grade of diamonds so you are assured that the stone you buy will have proportions that are either perfect or close to being perfect, in order to maximise its brilliance.

There are about 10 common diamond shapes or diamond cut varieties. These can be divided into two broad divisions - the round brilliant shape or the fancy shape. About 75% of all diamonds that are sold are round. The mechanics of the round shape maximises the diamond’s brightness.

Of the fancy shapes, the Oval cut, then princess cut is most popular and is most often chosen for engagement rings. Both cuts work very well for a wide variety of ring styles. When choosing the shape of a diamond, you need to think of the personal preferences of the person you are buying it for.

Learn more about Diamond Cut in our guide dedicated to the topic.


Diamond Carat

Again, based on the person’s preference, select a carat weight or at least the minimum carat weight you want to buy. The ‘carat’ is not the size of the diamond, it is the standard measure used for the weight of a diamond. The carat of a diamond will give you a good indication of its value. The higher the carat, the higher the value. But the diamond carat is not the only determiner of its value.

Cut grade is also important to consider here. Two stones of the same carat can have a deep cut or a shallow cut both of which influences the brilliance of the diamond. So it is very important to choose a stone with high cut grade in addition to good carat weight. Explore in more detail in our guide on Diamond Carat

Diamond Clarity

As diamonds are naturally occurring stones that are formed deep inside the earth, humans cannot control the process or its result. So, almost all diamonds have ‘birthmarks’ in the form of blemishes or inclusions. Flawless diamonds are extremely rare and priced incredibly high. Most blemishes are not visible unless magnified but these do influence the reflection of light within the diamond. This is the reason that the clarity grade of a stone has an impact on its value and brilliance.

The GIA Clarity Grading Scale is used to rate the diamond clarity and this scale ranges from ‘Flawless’ (Fl) to ‘Slightly Included’ (S) and ‘Included’ (I). Stones that are rated 'Slightly Included' and above will not have inclusions that are visible to the naked eye. You can only see the inclusions in these stones with the help of a jeweller’s loupe. And stones that are graded over S12 are considered to be premium. Find more information in our detailed on Diamond Clarity


Diamond Colour

The colour of a diamond is probably the first thing you will notice, and it is decided by a variety of natural factors present when the stone is formed. Completely colourless diamonds are very rare as are naturally coloured diamonds.

The colours of a diamond are also graded according to a scale given by the Gemological Institute of America (GIA). ‘D’ marks colourless diamonds and the scale goes down to Z. As you go down the colour scale, the diamonds start to show a yellow or brown tinge. Most diamonds that are sold feature warm white or yellow shades. At Diamonds on Richmond, we recommend choosing a diamond between D - G colour. Explore Diamond Colour further in our in-depth guide. 


What’s the difference between a certification and an appraisal?

A certificate from an impartial laboratory gives you a grading report on the quality and characteristics of the diamond. This gives you the confidence that the features of the diamond are as the seller described. This independent evaluation of the diamond is important for insurance as well. But this certification of a stone’s qualities should not be confused with an appraisal.

An appraisal will determine the market value of the diamond. However, the certification of a diamond from a reputed laboratory is important for the appraisal process as well.

The Kimberly Process

When shopping for diamonds it is also important to understand the role of the Kimberly Process. The Kimberly Process is a multilateral trade regime that is committed to removing conflict diamonds from the supply chain, worldwide. Their Kimberly Process Certification Scheme has States implementing safeguards on rough diamond shipments and certifies them as ‘conflict-free’ stones. This assures the buyer that the rough diamonds in the shipment were not used to finance wars.

At Diamonds on Richmond, we have over 12 years of experience in guiding customers on diamond selection. Our focus on finding the perfect stone to fit your diamond ring requirements. We can help advise you on the 4 c's of diamonds, and choose the perfect gem or gems for you.

Book an appointment with us and we'll walk you through the process to find the perfect diamond.


At DOR we've made buying an engagement ring stress-free. Simply choose from our Collection, start with a proposal ring or customise one of our classic designs.


We've made it easy! Browse our designs, then tailor to your price point.


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