Diamonds are one of the most meaningful ways to celebrate life’s special moments, from engagements and weddings to anniversaries and personal milestones.

Diamond Buying Guide

Choosing the right diamond can feel complicated at first, but understanding a few key characteristics will help you make a confident decision.

The quality and value of a diamond are traditionally described using the 4Cs: carat, cut, colour and clarity. These factors influence how a diamond looks, how it sparkles and how rare it is.

However, the perfect diamond is not simply the one with the highest technical grades. The most important thing is choosing a stone that looks beautiful, suits the jewellery design and feels right for the person who will wear it.

This guide explains the most important aspects of diamond selection so you can choose your diamond jewellery with confidence.

Carat weight

Carat refers to the weight of a diamond, not its visual size. One carat equals 0.2 grams, and each carat is divided into 100 points. For example, a 0.75 carat diamond is often described as a 75-point diamond.

Diamonds between 0.30 and 0.75 carat are very popular as they provide a good balance of size, sparkle and value. Larger diamonds are much rarer in nature, which means their price increases significantly as the carat weight rises.

Although carat weight affects the overall size of a diamond, the cut and shape of the stone also influence how large it appears when worn. For example, oval and pear shaped diamonds often look larger than round diamonds of the same weight because their elongated shape creates a larger visible surface area.

Diamond cut

Cut is the factor that has the greatest influence on a diamond’s sparkle and brilliance.

Many people use the word “cut” to describe the shape of a diamond, but technically it refers to how well the diamond’s facets interact with light.

A well-cut diamond reflects light internally and disperses it through the top of the stone, creating the bright sparkle diamonds are known for.

Cut grading considers several factors including: Proportions, symmetry, polish and the relationship between the diamond’s depth and diameter.

Diamonds graded with excellent or very good cut proportions generally produce the most brilliance.

Diamond Colour

The highest quality diamonds are completely colourless, allowing light to pass through the stone without interference.

The GIA colour scale grades diamonds alphabetically from D (colourless) to Z (noticeable colour). Typically:

  • D–F: colourless
  • G–J: near colourless
  • K–M: faint colour

In many cases the difference between colour grades is extremely subtle and difficult to see without comparison stones. A near colourless diamond can still appear perfectly white once set in jewellery.

Diamond clarity

Clarity refers to the natural characteristics within a diamond, known as inclusions. These form during the diamond’s creation under intense heat and pressure deep within the earth.

Clarity grading evaluates:

  • > the number of inclusions
  • > their size
  • > their position within the diamond
  • > their visibility

The clarity scale ranges from Flawless (FL) to Included (I).

Most diamonds contain small inclusions, but many are invisible to the naked eye. Choosing a diamond with slight inclusions can often provide excellent value without affecting its beauty when worn.

Popular diamond shapes

The shape of a diamond refers to its overall outline rather than the technical quality of its cut. Different shapes create very different styles of jewellery. Some of the most popular diamond shapes include:

  1. Round Brilliant: The most classic and recognisable diamond shape, designed to maximise sparkle.
  2. Oval: An elegant elongated shape that often appears larger than a round diamond of the same carat weight.
  3. Princess Cut: A square diamond with sharp corners.
  4. Emerald Cut: Known for its distinctive step-cut facets.
  5. Pear Shape: A distinctive teardrop shape.

Other shapes such as cushion, marquise and asscher cuts offer distinctive alternatives for those seeking a unique engagement ring design.

Additional Diamond Characteristics

While the 4Cs are the primary factors used to evaluate diamonds, there are several other characteristics that can influence your decision.

Fluorescence

Some diamonds exhibit a soft glow known as fluorescence when exposed to ultraviolet light such as strong sunlight or UV lighting.

This effect is most commonly a faint blue glow that disappears when the UV light source is removed. Fluorescence does not necessarily improve or reduce a diamond’s beauty — it is simply another natural characteristic that some diamonds possess.

Diamond Certification

Many diamonds are supplied with a certificate issued by an independent gemological laboratory. The certificate confirms the diamond’s key characteristics and provides reassurance about its authenticity.

Two of the most respected diamond grading laboratories are:

  • Gemological Institute of America (GIA)
  • International Gemological Institute (IGI)

These certificates record the diamond’s cut, colour, clarity and carat weight and may also include diagrams showing any internal characteristics.

Natural diamonds and lab grown diamonds

Lab grown diamonds have become increasingly popular in recent years. Despite being created in a controlled laboratory environment rather than mined from the earth, they are chemically and visually identical to natural diamonds.

The main differences between natural and lab grown diamonds are: Their origin, environmental considerations, price and long-term resale value.

Lab grown diamonds typically offer excellent value for money, while natural diamonds are valued for their rarity and geological origin.

Both options can produce beautiful diamond jewellery, and the right choice often depends on personal preference and budget.

Choosing a diamond for an engagement ring

When selecting a diamond for an engagement ring, it’s helpful to consider how the stone will work within the overall design. Factors worth considering include: The style of ring setting, the wearer’s lifestyle, their preferred jewellery style - as well as how the diamond looks when worn on the hand.

For example, elongated diamond shapes can create the impression of a larger stone, while certain settings can enhance brilliance or protect delicate edges. Ultimately, the perfect diamond is one that balances beauty, quality and personal meaning.

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