The 4Cs explained
Carat, cut, colour and clarity — what each grade means and where the best value sits.
Typical UK second-hand price
1ct natural G/VS2 excellent cut: roughly £3,500–£6,500 second-hand
Carat
Carat is weight, not size: 1ct = 0.2 g. Prices jump at 'magic' weights (0.50, 0.75, 1.00, 1.50, 2.00ct), so a 0.95ct stone can cost noticeably less than a 1.00ct one while looking identical.
Cut
Cut decides sparkle and is the most important C. On round brilliants GIA grades Excellent to Poor; aim for Excellent (or IGI 'Ideal'). A poorly cut large stone can look smaller and duller than a well cut smaller one.
Colour
| Grade | Description | Best set in |
|---|---|---|
| D–F | Colourless | Platinum / white gold |
| G–H | Near colourless — the value sweet spot | Platinum / white gold |
| I–J | Near colourless, faint warmth | Yellow or rose gold |
| K–M | Faint yellow | Yellow gold, vintage pieces |
Clarity
| Grade | Meaning |
|---|---|
| FL / IF | Flawless / internally flawless |
| VVS1–VVS2 | Very, very slightly included |
| VS1–VS2 | Very slightly included — eye-clean |
| SI1–SI2 | Slightly included — SI1 often eye-clean |
| I1–I3 | Included, usually visible |
Before you buy
- Ask for the grading report number and check it on the lab's own website.
- Check the laser inscription on the girdle matches the report (use a loupe).
- Have any high-value piece checked by an independent valuer or jeweller before paying. JewelleryTrader does not authenticate items.
Frequently asked questions
Which of the 4Cs matters most?
Cut. It controls brilliance and fire; a well cut stone with lower colour or clarity often looks better than a poorly cut higher-grade one.
What clarity should I buy?
VS2 or a carefully chosen SI1 is usually eye-clean and gives the best value. Paying for VVS or flawless brings no visible difference.
More diamonds guides
Buying or selling a diamond?
Browse live adverts or list yours — private members get their first advert free.