The Diamond Buying Guide: How to Choose a Diamond

A diamond is the only thing most people buy at this price without knowing how it is priced. This guide is the whole process, in the order it actually matters, with nothing left vague. Read it once and you will be able to compare two stones on your own.

1. Start with the shape, not the specs

Shape is the only choice here that is purely about taste, so make it first and stop negotiating with yourself about it. Everything else in this guide is a trade-off; the shape is not.

Round brilliants return the most light and are the most forgiving of small compromises elsewhere — they are also the most expensive per carat, because cutting one wastes more of the rough. Every other shape is called a fancy shape and costs 15–35% less at the same weight.

• Round — maximum brilliance, highest price per carat
• Oval — looks larger than its weight, very forgiving
• Emerald — steps instead of sparkle, shows clarity honestly
• Pear and marquise — elongated, dramatic, need careful proportions
• Cushion — softer, warmer light return
• Princess and radiant — square outlines, radiant is the brighter of the two
• Asscher — a square emerald cut, architectural
• Heart — hardest to cut well, judge symmetry first

One practical note: elongated shapes — oval, pear, marquise — cover more finger for the same weight. If the visual size of the stone is what matters most, that is where your money goes furthest.

2. The 4Cs, in the order that actually changes what you see

Everyone learns the 4Cs as a list of four equal things. They are not equal. Ranked by how much they change the stone in front of you:

Cut — spend here

Cut is not the shape. It is how well the stone was proportioned and finished, and it is the only C that describes workmanship rather than raw material. A badly cut diamond leaks light out of the bottom instead of returning it to your eye, and no amount of colour or clarity grade rescues it.

On round diamonds, insist on Excellent (GIA) or Ideal/Excellent (IGI). On fancy shapes there is no official cut grade for the outline, so you judge by proportions and by looking at the stone: check the length-to-width ratio, and on ovals, pears and marquises look for a heavy dark band across the middle — the bow-tie. A faint one is normal. A strong one is a stone to skip.

Cut is where a smaller budget still buys something beautiful, and where a bigger budget is most often wasted.

Clarity — save here

Clarity grades the tiny inclusions inside the stone, under 10× magnification. Almost nobody looks at a ring under 10× magnification.

What matters is whether the stone is eye clean — no inclusion visible to the naked eye at normal distance. That is usually VS1 or VS2, and often SI1 depending on where the inclusions sit. Paying for VVS2 instead of VS2 on a round or a cushion buys you a number on a certificate, not a difference you can see.

The exception is step cuts. Emerald and Asscher cuts have large open facets that act like a window into the stone: there, go up a grade or two and check the plot on the report.

Colour — save carefully

Colour runs D (colourless) to Z (visibly tinted). D, E and F are colourless and priced accordingly. G to J are near-colourless: face up, in a ring, most people cannot tell G from D.

Two things shift this. Warmer metals hide warmth in the stone — in yellow or rose gold, H or I looks perfectly white, and paying for D is money spent on something the setting cancels out. And larger stones show colour more, so above roughly 2 carats it is worth moving up a grade.

Carat — the one everyone overpays for

Carat is weight, not size. Price jumps at the round numbers because demand jumps there: a 1.00 ct costs noticeably more than a 0.95 ct, and the two are indistinguishable on a hand. Buying just under a threshold — 0.90–0.95, 1.40–1.45, 1.90–1.95 — is the single easiest saving in this entire guide.

Spread matters more than weight anyway: a well-cut stone with a wide table looks bigger than a deep-cut heavier one. Compare the millimetre measurements on the report, not just the carat.

3. Natural or lab-grown

A lab-grown diamond is a diamond. Same carbon lattice, same hardness, same optical behaviour; a gemmologist needs specialised equipment to tell them apart. The difference is origin and price, and lab-grown typically costs a fraction of a natural stone of the same specification.

What that buys you is straightforward: at any given budget, lab-grown gets you a bigger, better-graded stone. What it costs you is resale and rarity — a natural diamond took a geological age to form and there is a finite quantity of it, and that is what part of its price represents.

Neither answer is wrong. What matters is that you decide deliberately rather than discovering it later. We label every stone and never mix the two.

Browse natural diamonds or lab-grown diamonds.

4. Never buy an uncertified stone

A grading report is an independent laboratory's opinion on the four grades above, plus measurements, proportions, fluorescence and a plot of the inclusions. Without one you are buying the seller's own description of their own goods.

• GIA — the strictest and most consistent, the reference standard for natural stones
• IGI — the dominant laboratory for lab-grown, widely used and reliable
• HRD — the Antwerp laboratory, well regarded in Europe

Grading is a judgement, not a measurement, and laboratories differ slightly in strictness. That matters when you compare two stones with the same grades from different labs — compare like with like.

Every diamond on this site carries a GIA, IGI or HRD report, and the report number is on the product page so you can verify it on the laboratory's own website before you spend anything.

5. Decide the budget before you fall in love with a stone

Ignore the “three months' salary” rule — it was an advertising line, not a tradition. Decide what you are comfortable spending, then optimise inside it.

The order of compromises that costs you the least visually:

1. Drop clarity to the eye-clean grade — usually free money
2. Drop colour to G–I, further in warm metals
3. Buy just under a carat threshold
4. Choose a fancy shape over round
5. Consider lab-grown
6. Never compromise on cut

Start from a budget band: under $1,000, $1,000–$2,500, $2,500–$5,000 or over $5,000.

6. Then choose the setting

The stone first, the setting second — the setting is what makes it a ring, but it is also what is easiest to change your mind about.

• Solitaire — nothing competes with the stone
• Halo — a ring of small stones makes the centre read larger
• Hidden halo — the same trick, visible only from the side
• Three stone — past, present, future
• Pavé — a band set with small diamonds
• Nature-inspired — vines, leaves, organic lines

Metal is mostly taste, with one practical consequence: white metals make a warm stone look warmer by contrast, yellow and rose gold make it look whiter. If you have chosen a G–J stone, a warm metal works in your favour.

7. Look at the actual stone before you pay

Two diamonds with identical certificates are not identical. Before you buy:

• Look at the individual stone, not a stock photo of the shape. Where the supplier provides it, our product pages have real photography and a 360° viewer you can rotate and zoom.
• Read the plot on the report and see where the inclusions sit — under a prong is very different from dead centre of the table.
• Check the millimetre measurements, not only the carat weight.
• Verify the report number on the laboratory's website.

What we do on our side

Every order ships free and fully insured within the United States, with an adult signature on delivery. You have 30 days to change your mind, with a prepaid insured return label at our expense — because a stone should be judged on your hand, not on a screen.

Still deciding? Browse all certified diamonds, read the frequently asked questions, or write to info@icondiamonds.com with your budget and what matters to you — we will shortlist stones and explain the trade-offs on each.