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Diamonds Buying Guide

With a radiance and beauty that will last a lifetime, diamonds make the perfect gift for friends, family – or yourself.


Buying diamonds might seem intimidating, but with the right information it can be a straightforward and exciting pursuit. A basic understanding of diamonds is necessary before you begin shopping, and this guide is meant to give you precisely that. In it you’ll learn about what jewellers refer to as the "Four Cs" of diamond grading, as well as diamond shapes.

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Four Cs of Diamond Quality

What is a diamond? A diamond is a crystal made up entirely of carbon atoms arranged in a cubic matrix. Diamonds come from deep within the Earth’s crust, formed by immense pressure. Their unrivalled hardness and high dispersion of light make diamonds useful for industrial purposes and of course desirable as jewellery. When considering a diamond experts and buyers refer to the Four Cs: Cut, Colour, Clarity, and Carat weight.


Cut is widely considered a diamond's most important characteristic. It has tremendous influence on a diamond's beauty. Many people confuse cut with the shape of the diamond. Unlike shape, diamond cut is the metric used to evaluate the precision and quality of the cutting itself, not the diamond’s overall shape.

Cut refers to the way a diamond is faceted to allow light to reflect from it. A facet is the polished flat surface of a diamond, which helps give it beauty, sparkle (also called ‘brilliance’) and fire (coloured light reflected from within a diamond). A diamond’s cut will determine its number of facets.

Cut also refers to a diamond's proportions, such as its depth and width and the uniformity of its facets – all characteristics that control its sparkle, brilliance, durability and other features we look for in a diamond.

A good cut is essential to a diamond's beauty. If a diamond has a poor cut its components don't interact with light as they should and will not display the sparkle of a diamond with a higher quality cut. The following is a list of the range of diamond cuts:

Ideal Cut

Reflects nearly all light that enters the diamond. An exquisite and rare cut.

Very Good Cut

Reflects nearly as much light as the ideal cut, but for a lower price.

Good Cut

Reflects most light that enters. Significantly less expensive than a very good cut.

Fair Cut

A quality diamond, but a fair cut will not be as brilliant as a good cut.

Poor Cut

Diamonds that are generally too deep and narrow or shallow and wide, losing most of the light out of the sides and bottom.


Colour refers to the presence or absence of colour in white – or clear – diamonds. The formation process of a diamond ensures that only an extremely rare few are totally colourless. Thus the whiter a diamond, the greater its value. Using the Gemological Institute of America’s (GIA) colour scale a D is the highest possible colour grade and is assigned to colourless white diamonds, while Z is the lowest and is assigned to those with a light yellow tint.

Diamonds also come in a wide variety of other colours, including red, green and a bright yellow known as "canary." These are graded as Z+ and are known as "fancy" diamonds. Ones with good colour are very rare and can sell for much more per carat than white diamonds. Black diamonds and blue diamonds have become sought-after fancy colours in recent years.


Clarity is a measure of the number and size of the tiny imperfections that occur in almost all diamonds. Many of these imperfections are microscopic, and do not really affect a diamond's beauty.

It is very common for diamonds to be formed with slight imperfections. These are known as "inclusions" and can come in many forms, including tiny white points, dark dots, or feathery cracks. The fewer inclusions, the more a diamond is worth. Its clarity ranking is determined by the number, size, type and placement of these inclusions.

Every diamond is unique and none are absolutely perfect under 10× magnification (the industry standard). The following GIA scale considers the size, nature, position, colour and quantity of clarity characteristics visible under 10× magnification.

F (Flawless)

Diamond has no internal or external inclusions.

IF (Internally Flawless)

Diamond has no internal inclusions and slight external inclusions.

VVS1-VVS2(Very Very Slightly Included)

Diamond has minute inclusions that are very difficult to detect under 10x magnification, even by an experienced grader.

VS1-VS2 (Very Slightly Included)

Diamond has minute inclusions that are invisible to the naked eye and seen only with difficulty under 10x magnification.

SI1-SI2 (Slightly Included)

Inclusions are invisible to the naked eye, yet easily seen by an experienced grader under 10x magnification.

I1-I3 (Included)

Inclusions are visible to the naked eye and affect brilliance.

Carat Weight

Carat is the term used to describe the weight of any gemstone, including diamonds. Each carat weighs 0.2 grams (roughly the same as a paperclip) and there are 100 points in each carat. So a 50-point diamond is a .50, or half, carat diamond. Expect to pay a premium for stones that are above a full carat weight. It’s important not to confuse ‘carat’ with ‘karat’, as in ‘14K gold,’ which refers to gold purity.

The abbreviation ‘ct’ is a shortened way to write carat, and refers to the weight of a single diamond. The abbreviation ‘ct tw’ indicates carat total weight, and is used to express the total weight when there are multiple diamonds in a piece of jewellery.

Larger diamonds are quite rare and in more demand than smaller diamonds of the same quality. Thus a one carat diamond solitaire ring (‘solitaire’ simply means a ring having one diamond) is nearly always more expensive than a ring made up of multiple diamonds that are similar, but smaller, even though they total one carat or more.


While not one of the 4 Cs, shape is something you will definitely want to consider when purchasing a diamond. Shape is not the same as cut. Whereas cut refers to the way a diamond was faceted to allow light to reflect from it, a diamond’s shape describes its overall design and form, mainly as viewed from above. When a shape is described it is sometimes referred to as a ‘cut’. The following are some popular cuts and shapes.

  • Princess: This cut is a square or rectangular design with numerous sparkling facets. The princess cut often finds its way into wedding rings and solitaire engagement rings.
  • Round Brilliant: Another popular cut, accounting for well over the majority of diamonds sold. The “brilliant” cuts have exactly 58 facets and come in a variety of shapes.
  • Marquise-cut: This shape can maximize carat weight, giving you a larger-looking diamond. This brilliant-cut diamond makes fingers appear long and slender.
  • Emerald-cut: What makes this shape different is its pavilion (the bottom part of the diamond), which is cut with rectangular facets for a unique optical appearance. This shape calls attention to the clarity of a diamond.
  • Oval shape: With a stunning brilliance similar to a round diamond, oval diamonds are also very popular as their length can help accentuate long, slender fingers.
  • Pear shape: This brilliant-cut diamond, sometimes referred to as ‘teardrop’, is a popular choice for diamond jewellery. An elongated pear shape creates a subtle slimming effect on the fingers.
  • Heart shape: This shape is perfect for romantic gifts and expressions of love. A favourite for anniversaries and special occasions.