How to Choose a Diamond: Step-By-Step Guide

Last updated on December 27, 2022

With a large selection of diamonds available on the market, buyers often get confused about how to choose a diamond. However, there are some simple rules for selecting a good stone that are brought together in this step-by-step guide.

Choose a Shape and Set a Budget

First things first, you should decide what diamond shape is more desirable for you.

As the most popular diamond shape is round, let’s take it as a reference while selecting the best stone for further steps as well. Most recommendations in this guide also apply to other shapes, but for more specific guidelines on colour, clarity, and cut grades, check out the following links: round, oval, pear, marquise, cushion, emerald, Asscher, princess, radiant and heart.

Most likely, you already have an idea of how much you can spend on your diamond. However, you should also remember about any import duties if ordering from overseas, taxes and shipping fees. Do not forget that your total budget includes the prices of both the diamond and fees.

Think about what you can afford to spend. Start your diamond selection process by filtering out the diamonds that fall out of your budget. This will help you save time and effort.

Decide on Carat Weight and Cut Quality

After you set your budget, you can decide on the carat weight of the stone. Most people try to buy the biggest diamond they can get for their money. However, it is recommended to start working with a carat range and narrow down your choices later.

Cut quality should be a priority over the other characteristics, as it determines how light enters the stone and is reflected back. The better a diamond’s cut, the more brilliance and sparkle the stone has.

The Gemological Institute of America (GIA) grades round brilliant diamonds on a five-point scale of Excellent, Very Good, Good, Fair and Poor, where Excellent cut grade diamonds provide the maximum brilliance and sparkle.

A diamond with no inclusions or colour tints will still look dull if it is not cut exceptionally well, which is why you should always opt for the best cut quality.

Set Minimum Colour

Diamond colour is graded using a scale developed by the GIA (Gemological Institute of America), which goes from D to Z, with D being the most colourless and Z containing yellow or brown tints noticeable to the naked eye.

Each letter grade falls under a clearly defined range of colour appearance:

• D-E-F – colourless
• G-H-I-J – near colourless
• K-L-M – faint
• N-R – very light
• S-Z – light

If your diamond is set in platinum or white gold, the colour minimum should be at least an I colour. The stones any lower will show yellowish or brownish tints. However, there is an exception to every rule. If you are going to have your diamond set in a setting other than solitaire (side-stone setting, pavé setting, halo setting, etc.), the minimum should be H colour.

If the diamond is set in yellow or rose gold, you can go as low as J, K or even L colours. Diamonds tend to absorb the colour of their setting, meaning you will barely see the difference between H and K colour diamonds once set.

Set Minimum Clarity

The next step is to decide on the minimum clarity range. According to the Gemological Institute of America (GIA), diamond clarity is graded on the following scale:

• FL (Flawless) – no inclusions and blemishes visible under 10x magnification.
• IF (Internally Flawless) – no inclusions visible under 10x magnification.
• VVS1, VVS2 (Very Very Slightly Included) – hardly noticeable and very small inclusions visible under a gemological microscope.
• VS1, VS2 (Very Slightly Included) – minor inclusions visible with effort under 10x magnification.
• SI1 and SI2 (Slightly Included) – easily noticeable inclusions under 10x magnification.
• I1, I2 and I3 (Included) – obvious inclusions visible to the naked eye.

To have a stone that looks clean to the naked eye, set the lower end of your clarity range at SI1. You can also find an eye-clean diamond in the SI2 range, but you will need to sort through more diamonds until you find the right one.

Examine Additional Characteristics

Now it is time to examine additional features you should be paying attention to.

Fluorescence

Diamond fluorescence is the ability of a stone to emit light and change its colour when subjected to ultraviolet (UV) rays. It is described by its intensity on the following scale: None, Faint, Medium, Strong and Very Strong.

Although fluorescence does not affect the quality of a diamond for an average observer, it is recommended to choose a stone with either a None or Faint fluorescence level. Stones with Strong fluorescence will appear hazy under normal light. Stones with Medium fluorescence usually look fine, but to be on the safe side, avoid Medium fluorescence diamonds if they are in the D-E-F-G range. However, for diamonds with H colour or lower, Medium fluorescence can improve colour, making them appear whiter.

Culet

The culet is a small facet at the bottom of a diamond placed parallel to the table. It prevents chipping and abrasion to the point.

The culet is described according to its size using the following grades: None, Very Small, Small, Medium, Slightly Large, Large, Very Large and Extremely Large. When there is no culet, it may be indicated as a pointed culet.

Make sure that the diamond you are going to buy has None to Small culet size. Bigger culets will be visible through the stone’s top and look like dark holes.

Girdle Thickness

The girdle is the middle portion of a diamond, a narrow section separating the crown from the pavilion. It is graded using the following eight-grade scale: Extremely Thin, Very Thin, Thin, Medium, Slightly Thick, Thick, Very Thick and Extremely Thick.

Girdle thickness should fall within the Very Thin to Slightly Thick grade range. However, Very Thin girdles are at higher risk of chipping, while too thick girdles negatively affect a diamond’s proportions.

Featured image: Wirachai Moontha / Canva