A Guide to Diamond Engagement Rings

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How to Judge the Quality of Diamond Engagement Rings

Diamond has always remained the most popular stone for engagement rings with good reason. Regardless of how you feel about the tradition of diamond engagement rings, it’s hard to argue against diamond being the ultimate symbol of something which is formed by fate and lasts into eternity; the ultimate symbol of healthy love and partnership.

Symbols aside however, not all diamond engagement rings are created equal. To judge the quality of any given diamond, a standardised model was developed by the GIA called the 4 C’s.

Understanding the GIA 4 C's

The 4 C’s is a diamond judgement convention established by the Gemological Institute of America as a way for all diamonds to be ranked globally by quality factors on a unified scale. GIA is the Largest, Most Respected Nonprofit Source of Gemological Knowledge in the World.

When selecting a diamond for an engagement ring or for any piece of jewellery, it’s important for you to understand how this standard of quality judgement works and why your diamond costs what it does.

So what do the 4 C’s mean?

The 1st C: CUT

Cut refers to the precision of the of the facets (or faces) on a diamond. Each little flat edge on a diamond and the edges which join them are carefully created by diamond manufactures. These flat surfaces contribute to sparkle, colour and the overall elegance of the diamond.

Well-cut diamond engagement rings will internally reflect light from one mirror-like facet to another and reflect it through the top of the stone. This will display a brilliance and fire, thereby placing well-cut diamonds higher on the Diamond Quality Pyramid than deep or shallow-cut diamonds. Diamonds that are cut too deep or too shallow lose the light through the side or bottom of the stone resulting in less brilliance and eventually, value.

Non-round shaped diamonds, also known as fancy shapes, will have their own guidelines to be considered well-cut.

Diamonds with excellent cut quality will have equally proportioned facets, angles which correctly capture light, no thick edges between the facets and near perfect symmetry.

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The 2nd C: CLARITY

The clarity factor is exactly as it sounds; how transparent and free of blemishes is the diamond? Because mined diamonds are naturally formed in the earth, they of course often have other trace minerals in their structure which causes imperfections. These imperfection can appear as a general cloudiness or as dark flecks caught within. The clarity of a diamond determines how well light passes through and by extension, how nicely the diamond captures light.

Clarity is the second important factor to consider when buying diamond engagement rings. The scale begins at internally flawless (IF) and proceeds through several grades of clarity depending on the size and number of inclusions present in a stone.

An excellent quality diamond will have near perfect clarity, with no visible specks to the naked eye and with enough transparency to see right through the diamond.

Officially, the GIA Diamond Clarity Scale has 6 groups which diamonds fall into for calrity:

The 3rd C: COLOUR

Colour can often be a little bit subjective, as in some instances, colour is a desirable quality. Against the global standard of quality though, true diamonds are considered to be colourless, as colour originates from flaws in the atomic lattice or from the intrusion of other minerals in the structure.

These fancy coloured diamonds (such as yellows, pinks, and blues) are graded on a separate colour scale. Colourlessness in true diamonds is considered desirable because it captures the ambient light with more accuracy and purity, meaning you get a more beautiful display of fire (multicoloured scintillation) and interaction with their environment.

An excellent quality diamond should appear to have no colour tint when held against a pure white background.

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Officially, diamonds are judged by the GIA for colour on an alphabetical scale ranging from D to Z, with Z being the poorest colour quality:

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The 4th C: CARAT

Carat is the final factor which determines the quality and most importantly, the cost of a diamond. Carat is a measurement of weight for diamonds which essentially describes the size. As a result, carat operates as a multiplying force with the other 3 C’s. Ultimately carat is the factor which will likely be the most impactful on your budget, so it’s important to find a balance which captures both the size you would like and how well it scores on the other factors. But the size of the diamond is ultimately up to you.

As the carat of the diamond goes up, so does the price, especially when the other factors remain high scoring.

The 5th Element: SHAPE

Cut and shape are often confused together. An easy way to remember the difference is to recall the small & big picture.

  • The small picture is each cut made on the surface of the gemstone
  • The big picture is the total final shape, the outline of the gem as a whole

Shape refers to the big picture of the diamond, the total final outline of the stone. These shapes include:

  • RBC- Round Brilliant Cut
  • OVAL
  • PEAR


Round Brilliant Cut is the most popular diamond shape. Almost 75% of all sold diamonds are RBC. It’s a classic and timeless choice that never goes out of style. All the rest of the cuts are called fancy diamond shapes.

Round diamonds cost more on a per carat basis than fancy shapes for two reasons: the demand for round diamonds is very high, and the yield is relatively low. Because more of the rough stone is lost in the cutting of a round diamond, the cost of each carat retained is higher. A typical round diamond (for example, a 1.00 carat, F-colour, VS2-clarity, excellent cut) may cost 25-35% more than a similar fancy shape diamond.

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For more in depth advice on diamond engagement rings, call us and speak to one of our Canberra local jewellery specialists.

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