The 4Cs are cut, colour, clarity and carat weight. They are the four qualities the Gemological Institute of America uses as a shared language for describing a diamond, and they are the first things we read on a report when we shortlist stones with you. No single C tells the whole story. We look at all four together, then at the diamond itself on a video consultation, before you approve anything in writing.
Cut
Cut describes how a diamond's facets are proportioned and finished, and how that work affects the light you see. GIA treats cut as the factor that most affects a diamond's appearance. For a standard round brilliant, GIA publishes a cut grade that takes brightness, fire and scintillation into account, along with design and craftsmanship. Most fancy shapes do not receive that same cut grade, so for an oval, a cushion or a pear we still look carefully at the face up appearance with you. Our guides to why cut matters and to brilliance, fire and scintillation explain that in more detail.
Colour and clarity
On a GIA report for a natural diamond, colour is graded from D, which is colourless, through to Z, where a yellow or brown tint becomes easier to see. Clarity is graded from FL, or flawless, through to I3. Many beautiful diamonds sit well below the top of each scale. What matters is whether any tint or any inclusion is noticeable in the hand and in the setting you have in mind, not whether the letters look impressive on paper. Our diamond colour chart and our clarity scale explained set out those grades in plain English.
Lighting changes what you notice. A stone can look colder in one room and warmer in another. An inclusion that is obvious under a loupe may be very hard to see when the ring is on the finger. That is why we would rather show you the diamond than ask you to choose from grades alone.
Carat weight
Carat is a measure of weight, not of how large a diamond looks. GIA defines one carat as 200 milligrams. Two stones of the same carat weight can look quite different in outline if one is cut deeper or has a more elongated shape. The millimetre measurements on the report, and a view of the stone itself, tell you more about presence on the hand than the carat number alone.
We work by video consultation and message. We will talk through the 4Cs, share photographs or a live view of shortlisted stones, and agree the setting around the one you choose. Nothing is made until you approve the design and the stone in writing. A 70 percent deposit is paid then, making time is 5 to 6 weeks, and the ring is UK hallmarked before insured, tracked FedEx delivery. If you would like to start that conversation, get in touch, browse the diamonds we can source, or read our guide to how to read a GIA certificate.
Frequently asked questions
What are the 4Cs of a diamond?
They are cut, colour, clarity and carat weight, the four qualities GIA uses as a shared language for describing a diamond. We look at all four together, rather than treating any one of them as the only thing that matters.
Which of the 4Cs matters most?
GIA treats cut as the factor that most affects how a diamond returns light. Colour, clarity and carat still matter, and the right balance depends on the shape, the setting and what you care about seeing in the hand.
Do the 4Cs appear on a grading report?
On a GIA report for a natural diamond, you will find the colour and clarity grades, the carat weight and, for a standard round brilliant, a cut grade. For fancy shapes the measurements, polish and symmetry are still recorded even when a cut grade is not.
Do you talk through the 4Cs before making begins?
Yes. We look at stones with you on a video consultation, and nothing is made until you approve the design and the stone in writing. A 70 percent deposit is paid then, and making time is 5 to 6 weeks.