Choosing a Diamond

Following on from our article last week about deciding on a budget for your diamond engagement ring the next thing you need to consider is the diamond itself. Diamond is the traditional choice for engagement rings and is the most popular choice for the centre gem. Diamonds come in a multitude of different shapes and each one is different in terms of size and quality so making sure you know what shape your partner prefers and striking a balance between what size diamond you can get within your budget and that diamonds quality (cut, colour and clarity) will be important.

Diamond Shape

A diamonds shape is an important factor to consider when choosing a diamond engagement ring for someone as they will likely have strong opinions on what they like and more importantly what they don’t like. Shape and cut are terms that are used interchangeably however, they are actually quite different. Cut relates to the facet patterns that are cut into the raw diamond to shape it. Shape refers to the physical shape of the diamond of which there are two kinds – round and fancy shapes.

Round diamonds are by far the most popular of the different diamond shapes and are superior to all other shapes in terms of light reflection, the round shape also maximises the potential brightness of the diamond. The shape was invented circa 1900 and consists of 58 facets placed precisely using a mathematical formula to optimise fire, brilliance and scintillation, the facets are distributed among the crown (top), girdle (middle), and pavilion (base).

All non-round diamond shapes are referred to as ‘fancy’ shapes of which there are several including: oval, marquise, pear, heart, asscher, radiant, cushion, emerald and princess cuts. The princess cut is the most popular of the non-round shapes and is a relatively new shape having been invented in 1980.

Before choosing a diamond for your diamond engagement ring make sure you have a good idea of the shape of diamond that your partner prefers.

Size & Quality

The final set of considerations when buying a diamond are the size of that diamond and its quality. These set of considerations are nearly always referred to as The 4 C’s, carat, cut, colour and clarity. Each of these factors affect the diamonds price so you need to determine what is most important to you (and your partner) given your budget. Many start with size as this is the most visually apparent of the four.

Diamond Size

Carat is often confused with physical size but it actually describes the weight of a diamond. It is however, a good approximation of the size of a diamond as obviously a 2 carat diamond will be larger than a 1 carat diamond.

Each carat is 0.2 grams and is divided up into 100 points of 2 milligrams each. The weight of smaller diamonds under 1ct is always expressed in points, e.g. a half carat diamond would be described as a 50 point diamond or a 50 pointer.

Buying Tips

Go for diamond just below the most popular carat weights as these are typically sold at a discount but will be visually indistinguishable from the larger size. E.g. go for a 0.9ct instead of a 1ct stone as it will cost less but look exactly the same as a 1ct stone.

Understanding Diamond Quality

Once you have decided on the size of your diamond you need to consider its quality. There are 3 factors affecting a diamonds quality:

  • Cut

  • Colour

  • Clarity

All three are measured by scales developed by the Gemmological Institute of America – an independent diamond grading laboratory that grades the size and the quality of diamonds. The higher up on each scale you go the more the price of your diamond will increase.


A diamonds cut is the most important quality characteristic of a diamond. Cut does not refer to a diamonds shape but rather to its proportions, symmetry and polish. Cut is a measure of a diamonds light performance or what we think of as ‘sparkle’. If the workmanship of the diamonds cut is poor the diamond will look dull and lifeless.

If the cut is too shallow light will leak out of the bottom of the stone. If it’s too deep light is refracted out the sides. When the diamond is cut with proper proportions light is reflected out of the top (crown) of the diamond and into the eye of the observer. This reflected light is perceived in 3 different forms:

  • Scintillation: The flashes of light or sparkle when a diamond or a light source is moved.
  • Fire: The dispersion of light in the colours of the visible spectrum – seen as flashes of colour.
  • Brilliance: The brightness created by the combination of all the white light reflections from the surface and inside of the polished diamond.

Choosing a high cut grade maximises the beauty of a diamond for a given carat weight.

Cut Grading System

The GIA cut grading system assigns one of five grades to describe the overall quality of a diamonds cut:

  • Excellent: Maximum fire and brilliance, this diamond will reflect nearly all the light that enters it creating exceptional sparkle and life.
  • Very Good: A diamond with a cut grade of Very Good will reflect most of the light that enters it producing superior fire and brilliance. Appears very similar to a diamond with an ‘Excellent’ cut but will have a lower price.
  • Good: Reflects a good deal of the light that enters the diamond giving an above average appearance. The ‘Good’ grade is excellent value compared to higher cut grades.
  • Fair: Allows a lot of light entering the diamond to escape from the sides or bottom reducing fire and brilliance.
  • Poor: Allows the majority of light entering the diamond to escape through the sides or the bottom making the diamond appear noticeably dull or lifeless.
Buying Tips

Look for diamonds with a cut grade from the GIA and select the highest cut grade that your budget will allow. Diamonds with a cut grade of “Good” or “Very Good” are an excellent combination of beauty and value. Be sure to avoid diamonds with a cut grading of “Poor”.


Colour refers to a diamonds lack of colour and grades the whiteness of a diamond. The whiter the diamond the less colour it will have and the better the colour grade will be.

Colour Grading System

A diamonds colour is graded using a letter scale from D to Z with D being the highest/best possible grade and Z being the lowest/worst.

  • D – F : Colourless – The highest colour grade, extremely rare
  • G – J : Near colourless – Colour difficult to detect unless compared side by side against diamonds of better grades. Excellent value.
  • K – M : Yellow Tinge – slightly detectable warmth or tone, still good value.
  • N – Z : Light Yellow – stones with these colour grades will have noticeable colour which will be visible to the naked eye. Not generally desirable.
  • Fancy : These are diamonds with an intense yellow or brown colour – these are graded separately on their own scale.
Buying Tips

For an excellent value diamond with little or no colour visible to the naked eye look for a diamond with a near colourless grade of G – I. If you are a purist and want colourless diamonds go for grades of D, E & F but bear in mind that this will push up the price significantly. The visible difference between diamonds of one colour grade and the next, for example G to H or I to J is so minor it is difficult to detect with the unaided eye. The cost savings however can be significant. Keep in mind that as the diamond size increases the colour becomes more noticeable. This is especially important to remember when buying larger sized diamonds of 2 carats or more. Diamond shapes that reflect more light (i.e. have more sparkle) such as round or princess can mask some colour in a diamond.


Most diamonds have some imperfections known as inclusions or blemishes. Clarity measures how clear the diamond is to the naked eye by a trained gemmologist and under 10x magnification.

Clarity Grading System

Diamonds are graded for clarity using the 11 point diamond clarity scale developed by the Gemological Institute of America

  • FL – Flawless: No inclusions or blemishes are visible to a gemologist using a 10x microscope. Extremely rare, very expensive.
  • IF – Internally Flawless: No inclusions only blemishes are visible to a gemologist using a 10x microscope. FL & IF diamonds appear identical unless viewed by a gemologist under a 10x microscope.
  • VVS1/VVS2 – Very Very Slightly Included: Inclusions are present but are difficult for a gemmologist to see using a 10x microscope. Inclusions are invisible to the naked eye but will be visible to a gemologist using a 10x microscope.
  • VS1/VS2 – Very Slightly Included: Inclusions are visible to a gemmologist under a 10x microscope but are minor. Inclusions are still invisible to the naked eye but will be readily visible to a gemologist using a 10x microscope.
  • SI1/SI2 – Slightly Included: Inclusions are visible to a gemologist using a 10x microscope. Often invisible to the naked eye but some (especially SI2) will be visible.
  • I1/I2/I3 – Included: Inclusions are obvious to a gemologist using a 10x microscope. Inclusions are almost always visible to the naked eye and are often pronounced. Not typically carried by most diamond dealers.
Buying Tips

If you don’t want any imperfections in your diamond, even ones you cannot see, then choose diamonds with a clarity grade of VVS2 or better. Bear in mind that these are the rarest of an already rare material so be prepared to pay high prices. A good compromise in terms of clarity grade and value is the VS1/VS2 range which appear flawless to the naked eye.

Remember, the larger the diamond is the easier imperfections are to detect. For diamonds over 2 carats, a clarity grade of VS2 or higher is best for avoiding any inclusions visible to the naked eye. For diamonds between 1 and 2 carats, clarity grades of SI1 or better will not have inclusions readily visible to the naked eye. For diamonds under 1ct, clarity should be considered the least important of the 4Cs.

Final Thoughts

Whew! That was a lot to take in – well done on making it this far 🙂 Remember that diamond shopping is all about striking a balance between size and quality within your budget and of course getting the right shape for your partner. In our next article we deal with the different style’s of setting available once you have your diamond.

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