Diamond Grading – The 4C’s

Let’s start with the basics

Many people are confused about how diamonds are priced. The best explanation is that asking for the price of a diamond is like asking for the price of a house. A real estate agent can’t quote you a price for a house without knowing its size, condition, location, etc. This process is the same one used when buying a diamond. A diamond’s rarity and price depend on the interplay of all the 4Cs – cut, clarity, carat, and colour.


Diamonds are graded on a colour scale established by the Gemological Institute of America (GIA) which ranges from D (colourless) to Z. Warmer coloured diamonds (K–Z) are particularly desirable when set in yellow gold. Icy winter whites (D–J) look stunning set in white gold or platinum.

TIP: We’ll happily show you a variety of colour grades next to one another to help you determine your colour preference.


Clarity refers to the presence of inclusions in a diamond.

Inclusions are ranked on a scale of perfection, that was established by the Gemological Institute of America (GIA). The clarity scale, ranging from F (Flawless) to Included (I), is based on the visibility of inclusions at a magnification of 10x.

TIP: Some inclusions can be hidden by a mounting, thus having little effect on the beauty of a diamond.

Carat Weight

Diamonds and other gemstones are weighed in metric carats: one carat is equal to 0.2 grams, about the same weight as a paperclip. (Don’t confuse carat with karat, as in “18K gold,” which refers to gold purity.)

Just as a dollar is divided into 100 pennies, a carat is divided into 100 points. For example, a 50-point diamond weighs 0.50 carats.

TIP: The majority of diamonds used in fine jewellery weigh one carat or less.


Nature determines so much about a diamond, but it takes a master cutter to reveal the stone’s true brilliance, fire and ultimate beauty.

Based on scientific formulas, a well-cut diamond will internally reflect light from one mirror-like facet to another and disperse and reflect it through the top of the stone. This results in a display of brilliance and fire, thereby placing well-cut diamonds higher on the Diamond Quality Pyramid than deep or shallow-cut diamonds.

TIP: Since a round diamond is symmetrical and capable of reflecting nearly all the light that enters, it is the most brilliant of all diamond shapes.

Three important things to remember


The 4Cs are used throughout the world to classify the rarity of diamonds. At Randor Jewellery we sell GIA certified loose diamonds with trusted diamond grading reports to ensure you’re getting exactly the quality of diamond you’re paying for.


Diamonds with the combination of the highest 4C ratings are rarer and, consequently, more expensive. Our diamond experts are experienced in showing you how to get the best value possible for every style of ring and budget!


No one C is more important than another in terms of beauty – it’s personal preference. If you’re looking for advice, we’ve got years matching the right mix of 4 C’s to the perfect custom ring setting.

We’ll show you all you need to know.

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