Diamond Buying Guide

Here's a thing that doesn't get said enough at the start of diamond conversations: a diamond is pure carbon. That's it. Pure carbon, squeezed under unimaginable heat and pressure about 100 miles beneath the earth's surface, over the course of billions of years, before being blasted upward by volcanic activity and eventually, ending up on your finger. The oldest diamonds on earth are around 3.5 billion years old. That's the romance of a natural diamond, and it's real.

For most of human history, if you wanted a diamond, it came from the ground. That changed in the 1950s, when scientists figured out how to grow them in a lab, and in the last decade especially, lab grown diamonds have gone from niche curiosity to completely mainstream.

Here's what matters: a lab grown diamond is a real diamond. Same carbon structure, same hardness, same optical properties, same sparkle. The only difference is origin and price. Lab grown diamonds typically cost 50–70% less than mined stones of equivalent quality. For couples who want a bigger, better stone for their budget, that's a pretty serious conversation-changer.

Natural or lab grown your call, and both are valid. What matters either way is understanding the 4 Cs, because that's how you buy a great diamond instead of just an expensive one.

If you take one thing from this entire guide, make it this: cut is everything.

Cut doesn't mean the shape of the diamond — round, oval, emerald, pear. Cut refers to how well the diamond has been fashioned from the rough stone. The proportions, the symmetry, the angles of the facets. A well-cut diamond takes incoming light, bounces it around the inside of the stone, and fires it back out through the top in a blaze of brilliance and fire. A poorly cut diamond leaks that light out the sides and bottom, and looks dull, flat, and lifeless as a result.

The GIA grades round brilliant diamonds on cut from Excellent down to Poor. For a round diamond, you want Excellent or Very Good, full stop. Don't compromise here. A slightly lower colour or clarity grade in a beautifully cut stone will almost always look better than a higher-graded stone with a mediocre cut. Cut is what makes a diamond alive.

For fancy shapes - ovals, emeralds, cushions, pears, the GIA doesn't issue an official cut grade, which makes things trickier. This is where buying from a knowledgeable jeweller who has already done the work of selecting well-proportioned stones is genuinely worth its weight in, well, diamond.

Diamonds are graded on colour from D (completely colourless) to Z (visibly yellow or brown). D, E, and F are the "colourless" tier — the best of the best. G through J is "near colourless." Below that, colour starts to become visible to the naked eye in most settings.

Here's the honest truth: most people cannot tell the difference between a D and a G with their naked eye. Once a diamond is set in a ring and on a hand, the colour differences at the top of the scale are essentially invisible unless you're a trained gemologist looking specifically for them.

For most shapes, a G or H colour hits the sweet spot - genuinely beautiful, bright, and white-looking in a ring, at a price that saves you significant money over D–F stones of the same quality in every other respect.

One nuance worth knowing: colour shows differently depending on shape. A round brilliant hides colour beautifully. An emerald cut, with its large open facets, shows colour more easily, so you might want to go a little higher, toward F or G. And if you're setting your diamond in yellow gold, colour matters even less, the warm metal flatters warmer stone tones and you can comfortably go lower on the scale without it showing.

Carat is simply a unit of weight. One carat equals 0.2 grams. That's it. It's not a measure of size, quality, or brilliance — just mass.

That said, carat weight is obviously related to size, and size is what people notice. So it matters. Just not in the way most people think.

A few things worth knowing:

Carat weight is not the same as visual size. Two diamonds of identical carat weight can look very different in size depending on how they're cut. A shallow, poorly cut 1ct diamond might actually have a wider face-up diameter than a well-cut 1ct — but the well-cut stone will look far more brilliant. Cut always wins.

Certain shapes look bigger per carat than others. Oval, pear, and marquise diamonds appear larger face-up than round brilliants of the same carat weight, because of how they distribute their weight across a longer, wider surface. This is genuinely useful budget information — if looking large is important to you, an oval or elongated fancy shape can get you there for less.

Magic numbers are a real thing — and working just under them saves serious money. Diamonds are priced in bands around popular carat milestones: 0.5ct, 0.75ct, 1ct, 1.5ct, 2ct. A 0.97ct diamond is visually indistinguishable from a 1.0ct, but it sits in a lower price bracket. This is one of the oldest tricks in the diamond-buying playbook, and it works.

Clarity refers to the presence of inclusions (internal characteristics) and blemishes (surface characteristics) in a diamond. The scale runs from Flawless (FL) at the top — essentially impossible to find in nature and priced accordingly — down through VVS1, VVS2, VS1, VS2, SI1, SI2, and into the Included (I) grades where inclusions are visible to the naked eye.

Here's the thing about clarity: the goal isn't a perfect diamond. The goal is an eye-clean diamond — one where you can't see any inclusions without magnification. And eye-clean doesn't require Flawless. Not even close.

For most round brilliants, an SI1 or SI2 can be eye-clean — the sparkle and light performance masks inclusions beautifully. For step cuts like emerald or Asscher, you need to go higher — VS2 or VS1 is the safer zone — because those open facets make inclusions far easier to see. Which is why, as we've said before, shape matters to how you allocate your budget.

The practical advice: always look at the diamond in person, or ask your jeweller to assess whether a stone is eye-clean before you buy. A VS2 that's eye-clean is genuinely as beautiful to wear as a Flawless stone — and the price difference between them is enormous.

In an ideal world, you'd max out every C. In the real world, you have a budget — so here's how to think about priorities.

Cut first, always. Don't compromise here. Everything else follows from cut quality.

Clarity second. Go for eye-clean over certified perfect. SI1 for rounds. VS2 for step cuts. Let your jeweller guide you.

Colour third. G or H is the sweet spot for most shapes and settings. Save the D–F budget for the cut and carat instead.

Carat weight last. Buy just under the milestone weights. Consider elongated shapes if size matters. And remember, a smaller, beautifully cut diamond will always outshine a larger, poorly cut one.

Numbers on a certificate only tell you so much. The thing that actually tells you whether a diamond is the one? Looking at it. Holding it. Seeing how it catches the light in a ring on your actual hand.

Our diamond advisors at our Dublin City Centre showroom love this stuff — genuinely — and they'll walk you through every C in real time, with real stones, until the choice is completely clear.

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