Diamond guide
What buyers look at
You don't need to be an expert to sell a diamond well — but understanding these characteristics makes offers much easier to compare.
Carat weight
Carat measures weight, not size: one carat is 0.2 grams. Value rises steeply rather than evenly with weight, and prices tend to jump at round milestones such as 1.00ct and 2.00ct. Two diamonds of identical weight can still be worth very different amounts.
Colour
Colourless diamonds are graded from D (colourless) through to Z (light yellow or brown). D to F is colourless, G to J is near-colourless and often excellent value. Fancy coloured diamonds — vivid yellows, pinks or blues — are graded on a separate scale and can be highly sought after.
Clarity
Clarity describes internal inclusions and surface blemishes, from FL (flawless) through IF, VVS, VS, SI to I. Many inclusions are invisible without magnification, so a VS or SI stone can look identical to the eye while costing considerably less.
Cut
Cut grades how well a diamond's proportions return light. It is the characteristic that most affects how a diamond actually looks. An Excellent cut can make a smaller diamond appear brighter and livelier than a larger, poorly cut one.
Shape
Round brilliant is the most traded and generally the most liquid shape. Fancy shapes — oval, cushion, emerald, pear, princess and others — depend more on individual proportions and on current demand among buyers.
Certification
A laboratory report from GIA, IGI or HRD independently records a diamond's characteristics. Buyers can offer with more confidence against a recognised report, which is why certified diamonds often attract firmer offers. An uncertified diamond can still be sold.
Fluorescence
Some diamonds glow under ultraviolet light. Faint fluorescence usually has little effect on value; strong fluorescence in a high-colour diamond can reduce it, and occasionally it slightly improves the appearance of lower colour grades.
Natural versus lab-grown
Natural diamonds formed over geological time; lab-grown diamonds are produced in weeks and trade in a separate market at substantially lower prices. CaratBid specialises in natural diamonds. If you are unsure which you have, a laboratory report will state it.
This guide is general information, not a valuation or advice on any individual diamond.