Diamond 4Cs Explained: Cut, Colour, Clarity & Carat — AT Jewels
Sunday, 20 September 2026 — the markets are shut for the weekend, so instead of a rate I want to sit down with you and explain the four things that actually decide what a diamond is worth: the 4Cs — cut, colour, clarity and carat.
In short: A diamond's price and its sparkle come down to four things jewellers call the 4Cs — Cut (how well it's shaped, which controls the sparkle), Colour (how close to colourless, graded D to Z), Clarity (how few natural marks it has, graded FL to I) and Carat (its weight). Of the four, cut does the most for how a diamond looks to the eye, so a well-cut stone that is a touch lower on colour or clarity often looks better — and costs less — than the numbers alone suggest. Always ask to see the certificate, and remember these grades are indicative; the piece in your hand is what matters.
The one C that matters most: Cut
People think carat is king, but if you ask me, cut is where the magic lives. Cut isn't the shape (round, oval, princess) — it's how precisely the diamond has been faceted and polished. A brilliantly cut stone catches light and throws it straight back at you; a poorly cut one of the exact same weight and colour can look dull and "sleepy" no matter how good the other numbers are. If you have to compromise on any of the 4Cs to stay within budget, my advice to every family who walks into AT Jewels is: never compromise on cut. It's the difference between a diamond that lives up to the moment and one that quietly disappoints.
Colour: closer to colourless, but you have room
Diamond colour is graded on a scale from D (completely colourless) down to Z (a visible yellow or brown tint). D, E and F are the "colourless" grades and carry the highest price; G through J are "near-colourless" and, once a stone is set in gold, most people cannot tell the difference with the naked eye. This is where a smart buyer saves money without anyone ever noticing. Interestingly, if you're setting a diamond in yellow or rose gold — as with a lot of the pieces we make — a slightly warmer stone (say G or H) can actually look lovelier against the metal than an icy D. Match the stone to the setting, not just to the certificate.
Clarity: what you can and can't see
Every natural diamond forms deep in the earth, so almost all of them carry tiny natural marks — jewellers call them "inclusions". Clarity grades run from FL (flawless) and IF, through VVS and VS, down to SI and I (where marks may be visible to the eye). Here's the honest truth: for most jewellery, a VS or a good SI stone is "eye-clean", meaning you simply cannot see any marks without a loupe. Paying a large premium to jump from VS to flawless rarely changes what your family or guests will ever see. Spend where it shows, save where it doesn't.
Carat: weight, not size — and why it jumps in price
Carat measures a diamond's weight, not its diameter. Two stones of the same carat can look different sizes depending on how they're cut. One thing worth knowing: price doesn't rise in a straight line with carat. A 1.00-carat diamond costs noticeably more than two 0.50-carat diamonds of the same quality, because larger single stones are rarer. So if total sparkle matters more to you than one big centre stone, a cluster or a pair of slightly smaller stones can give you a bigger look for less. Many of our earrings and pendants are designed exactly around that idea.
Certificates, hallmarks and lab-grown — the practical checks
Whatever you buy, ask for the diamond's grading certificate — it lists the 4Cs so you're not taking anyone's word for it. In India the gold that holds the diamond should also carry a BIS hallmark with its purity (14K, 18K and so on) and a HUID number. Lab-grown diamonds are increasingly popular in India in 2026 — they are real diamonds, chemically identical to mined ones, and are graded on the same 4Cs; they simply cost less and should always be clearly disclosed as lab-grown on the bill and certificate. Whichever you choose, insist that it's written down. GST on diamond jewellery is 3% (indicative and subject to change), and making charges vary piece to piece.
This weekend's featured pieces
A few diamond pieces from our Gold & Diamond collection — each one a real, certified stone set by our karigars. Tap any piece to see it up close.
Why buyers love these: Each stone is chosen the way I'd choose for my own family — a clean, lively cut first, with colour and clarity balanced sensibly against the setting so you're paying for what you can actually see. They're pieces made to be worn, not left in a locker.
Frequently asked
What are the 4Cs of a diamond?
The 4Cs are Cut, Colour, Clarity and Carat — the four qualities that together decide how a diamond looks and what it costs. Cut controls the sparkle, colour is graded D (colourless) to Z, clarity is graded FL down to I based on natural marks, and carat is the stone's weight.
Which of the 4Cs is most important when buying a diamond?
For most buyers, cut matters most, because it decides how much a diamond sparkles regardless of its size or grade. A well-cut stone that is slightly lower on colour or clarity usually looks better to the eye — and costs less — than a poorly cut stone with higher numbers.
Are lab-grown diamonds real diamonds?
Yes. Lab-grown diamonds are chemically and optically identical to mined diamonds and are graded on the same 4Cs; they typically cost less and should always be clearly disclosed as lab-grown on the certificate and bill so you know exactly what you're buying.
— Nitin Bardia / AT Jewels
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Disclaimer: This note is general information about diamond jewellery for buyers. Designs, availability and prices shown are indicative and subject to change; grading terms such as the 4Cs are explained in general and the actual grades of any piece are as stated on its certificate. The binding price for any gold or diamond purchase is AT Jewels' live counter rate at the time of billing. Please see the piece and its certificate in person before buying.