Like a woman, a good diamond is both beautiful and complex. Choosing one is no simple task—contrary to what one might think, it’s not all about size. In fact, four elements called the four Cs—carat, clarity, colour and cut—determine the quality and value of a diamond.
A unit of mass, a carat (ct) equals 200mg, or a fifth of a gram. Rings with multiple diamonds are measured by the carat total weight (ct TW) of all stones. Diamonds smaller than a carat are measured in ‘points’, with 100 points making up a carat.
A stone that reaches a full carat tends to have greater value than one that falls a little short—a 1.90 carat diamond will be more affordable relative to a full 2 carat rock, with no discernable difference once it’s set in a ring.
The clarity of a stone describes its flaws, known as inclusions and blemishes. Inclusions are flaws that occur inside the gem—specks of colour or cracks—while blemishes happen on the surface, often as a result of the cutting process.
The position of a flaw in relation to the setting (ie. how visible it is) is more important that its size. Clarity is graded from FL to I, based on flaws visible at 10x magnification:
FL Flawless: no inclusions or blemishes
IF Internally Flawless: no inclusions, slight blemishes
VVS Very, very slightly included. VVS1 has higher clarity than VVS2
VS Very slightly included. VS1 indicates higher clarity than VS2
SI Slightly included. Inclusions are noticeable to the trained eye. SI1 has higher clarity than SI2
I Included. Inclusions often visible to the naked eye and may compromise the stone’s durability. I1 indicates higher clarity than I2, which in turn is higher than I3
The term white diamond is a bit of a misnomer—they are in fact colourless, or at least they ought to be. Many have slight tints that affect their colour grading and value. Stones are graded from D to Z, based on their appearance at 10x magnification. Coloured diamonds are extremely rare (about one in 10,000) and graded and priced differently.
D, E, F Colourless
G, H, I Near Colourless
J, K, L, M Faint yellow tint
N, O, P, Q, R Light yellow tint visible to the naked eye
S, T, U, V, W, X, Y, Z Yellow to brownish tint, visible to the naked eye
Not to be confused with shape, cut refers to the stone’s proportions. Depth, width and symmetry of facets (the flat cut surfaces) determine the way light moves through a diamond, influencing its brilliance and durability. Too shallow and a diamond will appear dull, too deep and it will seem dark.