Know Your Diamond

A diamond's beauty comes down to physics — how it's cut, how it interacts with light, and how "clean" and colourless the crystal is. This guide breaks down what actually determines a diamond's quality and price, so you can prioritise what matters most for your budget.

Natural, Lab-Grown, and Simulated Diamonds

• Natural diamonds form over billions of years under intense heat and pressure deep within the earth, then are mined and cut.
• Lab-grown diamonds are chemically, physically, and optically identical to natural diamonds — the difference is that they're grown in a controlled lab environment over weeks rather than formed geologically. They're typically priced 30–50% lower than natural diamonds of comparable quality.
• Simulants (including cubic zirconia and moissanite, often loosely called "American diamond") are different materials entirely, designed to resemble a diamond's appearance at a much lower cost. They are not chemically diamond.

The 4Cs of Diamond Quality

Cut

Cut is widely considered the most important of the 4Cs for visual beauty. It describes how precisely a diamond's facets are proportioned and angled — not its shape. A well-cut diamond reflects light efficiently, producing the brilliance and sparkle diamonds are known for. A poorly cut diamond can look dull even with excellent colour and clarity.

Colour

Diamond colour is graded on a scale from D (completely colourless) to Z (noticeably yellow or brown tinted), developed by the GIA. Most jewellery uses diamonds in the D–J range; differences become harder to notice with the naked eye below G–H, especially in smaller stones or yellow-gold settings.

Clarity

Clarity measures internal characteristics called inclusions and external characteristics called blemishes, formed naturally as the diamond crystallised. Grades range from Flawless (FL) to Included (I1–I3). Many inclusions are invisible without 10x magnification — "eye-clean" stones in the VS–SI range offer strong value without visible flaws.

Carat

Carat measures a diamond's weight, not its visual size — 1 carat equals 200 milligrams. Two 1-carat diamonds can appear different sizes depending on their cut proportions and shape. Price increases disproportionately at certain carat thresholds (such as 1.00ct or 2.00ct), so a stone just under these marks can offer better value for a similar look.

The 4Cs at a Glance

C	What It Measures	Typical Sweet Spot
Cut	Light performance and proportions	Excellent / Very Good
Colour	Absence of colour tint	G–H
Clarity	Inclusions and blemishes	VS1–SI1 (eye-clean)
Carat	Weight	Just under round-number thresholds

Diamond Shapes

Shape refers to the diamond's outline — round, oval, cushion, emerald, princess, pear, marquise, and radiant are among the most common. Round brilliant is the most popular and generally the most expensive per carat due to cutting yield and light-performance efficiency; fancy shapes like oval and cushion can appear larger for the same carat weight because of how the weight is distributed across a longer or more open outline.

Certification

A diamond certificate (or grading report) from an independent laboratory such as GIA or IGI documents the 4Cs along with measurements, fluorescence, and additional characteristics, based on the specific stone rather than the setting. Always buy certified diamonds above roughly 0.30 carats, and match the certificate number engraved or referenced against the stone in front of you.

Fluorescence

Some diamonds emit a soft glow under ultraviolet light, called fluorescence, graded from None to Very Strong. In most cases, faint to medium fluorescence has no visible effect in normal lighting; in rare cases, strong fluorescence can make a diamond appear slightly hazy. It's a minor factor for most buyers but worth checking on the certificate for higher-value stones.

Inclusions: What's Normal?

Nearly every natural diamond has some microscopic inclusions — they're part of what makes each stone unique, and they don't necessarily affect appearance or durability. What matters is whether inclusions are visible to the naked eye and whether they're positioned where they could affect the stone's structural integrity — both of which a grading report and a trained jeweller can assess.

Buying Tips

• Prioritise cut quality first — it has the biggest impact on how a diamond actually looks.
• Choose "eye-clean" clarity (VS–SI range) rather than paying a premium for flawless grades invisible to the naked eye.
• Always verify the certificate matches the physical stone.
• Consider lab-grown diamonds if you want a larger stone within the same budget.

Cleaning and Storage

Clean diamond jewellery with warm water, a few drops of mild dish soap, and a soft brush to remove oil and everyday buildup that dulls sparkle, then rinse and dry with a lint-free cloth. Store diamond pieces separately in a fabric-lined box or individual pouches — diamonds are the hardest natural material and can scratch other jewellery, including other diamonds, if stored loosely together. See our full Jewellery Care guide for a complete maintenance routine.