The 4Cs of diamonds, and how to read a GIA certificate
A Graduate Gemologist explains what actually matters when you choose a diamond.
I trained as a Graduate Gemologist at the Gemological Institute of America, the organisation that created the 4Cs. Here is what each of them means, and which ones matter most when you are standing at the counter.
What are the 4Cs of a diamond?
Cut, colour, clarity and carat weight. Together they describe a diamond’s quality and largely determine its price. No single C makes a diamond beautiful; it is the balance between them.
Which of the 4Cs matters most?
Cut. It is the only C shaped entirely by human skill, and it decides how much light the diamond returns to your eye. A well-cut diamond of modest colour and clarity will often look more beautiful than a poorly cut stone with better grades. For round diamonds, GIA grades cut from Excellent to Poor. Aim for Excellent or Very Good.
How is diamond colour graded?
On a scale from D, completely colourless, to Z, light yellow or brown. D to F are colourless, G to J near-colourless. Set in yellow gold, a G, H or even I colour diamond looks white to most eyes and costs considerably less than a D.
What does clarity mean?
Clarity describes tiny internal features called inclusions and surface marks called blemishes. The scale runs from Flawless and Internally Flawless, through VVS1 and VVS2, VS1 and VS2, and SI1 and SI2, to I1, I2 and I3. Most VS and many SI diamonds are ‘eye-clean’: their inclusions cannot be seen without magnification.
What is carat weight?
Carat is weight, not size. One carat is 0.2 grams. Prices rise sharply at round numbers, so a 0.95 carat diamond can cost noticeably less than a 1.00 carat stone that looks almost identical.
How do I check a GIA certificate is genuine?
Every GIA report has a unique number, which is usually also laser-inscribed on the diamond’s girdle. Enter the number on GIA’s official Report Check website to see the original report. A jeweller can show you the inscription under magnification. The report also states clearly whether the diamond is natural or laboratory-grown.
My advice is always the same: put cut first, choose colour and clarity you cannot see with your own eyes, and spend the difference on a stone you love.
Questions about a stone or a piece? Message us on WhatsApp or visit the store on Shakespeare Sarani.