Diamond buying guide: how to choose a diamond

Carat weight and first impressions of sparkle alone are not enough to choose a diamond. Carat weight, cut, colour, clarity and the grading report together describe a diamond’s character.

The best choice is not necessarily the stone with the highest grades. Look for a balance of characteristics and consider how the stone works within the design.

This diamond buying guide explains what to look for and how the 4Cs can inform your choice.

What are the 4Cs of a diamond?

Four characteristics known as the 4Cs form the basis for choosing a diamond:

Carat weight, cut, colour and clarity.

Each of these characteristics contributes differently to the appearance and value of a diamond. Consider all four of the 4Cs together when assessing a diamond.

Carat: the weight of a diamond

Carat measures the weight of the stone. One carat equals 0.20 grams.

Carat weight and apparent size are different measures. Two diamonds of the same weight can look different in size from above because their shapes and cut proportions differ.

When choosing a solitaire diamond ring, consider the stone’s proportions and appearance in its setting as well as carat weight.

A higher carat weight does not always mean a better diamond. Balanced cut, colour and clarity often influence the overall appearance of a diamond more than carat weight alone.

Cut: what gives a diamond its brilliance

Cut directly affects how light enters and reflects from the diamond.

Light entering a well-proportioned diamond is redirected within the stone and returns through its upper surface. This makes the diamond look bright, lively and brilliant.

There is more to cut than the outline of the stone. Round, oval, pear and marquise describe shapes. Cut quality concerns the proportions of a stone and how it handles light.

When buying a diamond, consider how it handles light as well as its size.

How is diamond colour assessed?

Diamond colour grading assesses how noticeable the colour within the stone is.

The international diamond colour scale runs from D to Z. D is at the colourless end of the scale. Warm tones become more noticeable farther along the scale.

High colour grades such as D, E and F have a very white appearance. G and nearby grades can look very white to the eye in an appropriate design and metal.

The metal in which a diamond will be set also affects the choice of colour. A diamond’s colour can be more apparent in pale metals such as white gold. A range of colour grades can look harmonious in yellow gold.

Consider how the stone looks in the complete design before choosing a colour grade.

What is diamond clarity?

Natural diamonds can have tiny internal or external characteristics from their formation. Clarity is assessed by the number, position, size and visibility of these characteristics.

Clarity grades include VVS, VS and SI.

Many clarity characteristics in the VS range can be difficult to see with the unaided eye. In the SI range, visibility depends on the individual stone and the position of its clarity characteristics.

Look beyond the clarity grade on the report. Clarity characteristics can appear in different locations in stones of the same grade, affecting their appearance to the eye.

Consider the appearance of the diamond alongside the information on its grading report when choosing clarity.

Why does a diamond grading report matter?

A diamond grading report records the gemological characteristics of the stone following an independent assessment.

The report may include carat weight, colour and clarity grades and measurements of the stone.

GIA, HRD Antwerp and IGI are internationally recognised gemological institutions.

When buying a certified diamond, check that the report matches the stone and understand what its characteristics mean.

A report does not determine a diamond’s beauty, but it is a useful reference for understanding the characteristics of the stone.

Why can diamonds of the same carat weight have different prices?

A common misconception is that carat weight alone determines the price of a diamond.

Two diamonds of the same carat weight can have very different prices.

Colour, clarity, cut, proportions, shape and rarity all play a part.

Two diamonds weighing 1.00 ct each can have different values when their colour and clarity grades differ. Cut proportions can also alter the apparent brilliance and appearance of a stone.

Look at all of a diamond’s characteristics as well as its carat weight.

Design matters when choosing a diamond ring

A diamond with carefully chosen characteristics should also harmonise with its setting.

The position of the stone, the prongs, setting height and overall proportions affect how a diamond looks in a solitaire ring.

A different setting can make the same diamond look more delicate, more prominent or larger.

The choice of metal also alters the character of the design. White gold offers a bright, harmonious look. Yellow gold can give the diamond a stronger contrast.

When choosing a diamond ring, consider how it looks on the hand as well as the stone’s characteristics.

What should you look for when buying a diamond?

Begin by considering how the diamond will be worn and which characteristics matter most to you. Assess carat weight together with cut, colour and clarity. Check the grading report and, where possible, examine the stone itself as well as reading its measurements.

When choosing a diamond ring, consider the stone’s proportions, metal colour, setting construction and how it sits on the hand.

Look for a diamond whose characteristics are balanced, whose setting suits it and whose appearance feels right to you.

Balance for a timeless choice

Carat weight and report grades are only part of what makes a diamond special. The way a stone plays with light, its proportions and its relationship to the design give it character.

Rafi Roy Diamonds selects diamonds for their character, the proportions of the design and the appearance of the finished piece. A tradition of jewellery making dating back to 1905 combines with contemporary design to create timeless pieces.

Compare stones and settings in the diamond ring and solitaire collections at Rafi Roy Diamonds.