Beginner’s guide to diamond and the four Cs
Four English words decide what a diamond is worth. They simply do not weigh the same – and the fifth word, certificate, may weigh heaviest of all.
Carat – weight, not size
Carat is a measure of weight: 1 carat = 0.2 gram, divided into 100 points. A stone of 0.50 ct is called fifty points in the trade.
The price does not rise neatly with the weight but in jumps. Around round figures – 0.50, 0.75, 1.00 – there is a threshold: a stone of 1.01 ct can be considerably dearer per carat than one of 0.98 ct, while the difference is invisible to the naked eye.
Cut – the only C that comes from human hands
Colour, clarity and weight are settled at the mining. Cut – the cutting itself – is the only thing man adds, and it decides how the stone deals with light.
An excellently cut stone of middling colour often looks livelier than a moderately cut stone of better colour. With the brilliant cut the scale runs from Excellent through Very Good and Good to Fair and Poor.
Which of the four weighs heaviest? At equal weight, cut and clarity usually make the greatest difference to how the stone is experienced, while carat and colour work through most strongly in the price per carat. Which is precisely why a good valuer never judges them apart from one another.
Colour – how colourless is colourless
The colour scale runs from D (entirely colourless) to Z (clearly tinted yellow or brown). D to F is called colourless, G to J near colourless.
The difference between two neighbouring letters is invisible to a layman, certainly when the stone sits in a setting. In the price it is noticeable all the same.
Outside the scale fall the fancy colours: outspoken yellow, pink, blue or green. Those follow a market of their own, and a far higher one.
Clarity – what is inside the stone
- FL / IF – flawless, even under tenfold magnification. Rare.
- VVS1 / VVS2 – very, very small inclusions; barely to be found with a loupe.
- VS1 / VS2 – very small inclusions; visible with a loupe, not with the eye.
- SI1 / SI2 – small inclusions; clearly visible with a loupe.
- I1 / I2 / I3 – inclusions visible to the naked eye that can disturb the sparkle.
The certificate: the fifth C
A stone with a report from a recognised laboratory is demonstrably what it is. Without a report every buyer – ourselves included – has to hold a margin for uncertainty, and that pushes the price down.
The most widely respected laboratories are GIA, HRD and IGI. If you still have the report, bring it; the number is often laser-engraved into the girdle of the stone as well.
And then there is a distinction that decides everything: natural or laboratory-grown. Lab-grown diamond is chemically identical but has a completely different market and a far lower value. We always test for that, with older pieces too.
- Recognising hallmarks in jewellery585, 750, 925, EPNS – an overview of the most common hallmarks and what they mean.Read on
- Beginner’s guide to selling watchesBrand, reference, condition and papers. What a watchmaker looks at, and why that sets the price.Read on
- Beginner’s guide to silverFrom ducats to cutlery: which alloys there are, and when silver really brings in something.Read on
Questions about beginner’s guide to diamond and the four cs
What is my diamond worth without a certificate?
That we can assess at the table with a loupe and measuring equipment. Do reckon, though, on a stone without a report fetching less than the same stone with one: otherwise the buyer carries the risk of the assessment. We show you at the valuation how large that difference is.
Is a lab-grown diamond worth anything?
Chemically it is real diamond, but the market is a different one and the value sits considerably lower – and it has been falling for years, because production scales up easily. We always test whether a stone is natural or grown, and we tell you which of the two you have.
Should I have the stone taken out of the setting?
No, and above all do not do it yourself. We assess the stone in the setting; if taking it out is necessary for a precise determination, we do that expertly and with your permission. In practice that is rarely needed, because measuring formulas work well in the setting.
Do you also buy small diamonds out of jewellery?
Yes, but be honestly prepared: small decorative stones under roughly 0.10 carat generally have hardly any independent value. The value of such a piece then sits above all in the gold. We say so plainly rather than letting you expect an amount that is not there.
Is your question not listed? Ask it below, call 085 060 3009 or go to contact.
Still something unclear?
Ask it here. You will receive a personal reply by email, usually within one working day – no automated message and no phone call you did not ask for.
- An answer from a valuer, not from a template
- We keep your question so that you need not repeat anything
- No sales pitch afterwards
Rather just have it looked at?
A valuation is free and without obligation, at a location near you.