Choosing a Diamond: The 4Cs Explained Simply

Choosing a diamond means finding the right balance between four criteria and a budget. Here are our workshop’s guidelines for reading a diamond report and making an informed choice.

What is a diamond?

Diamond is crystallized carbon. It is the hardest natural mineral, at the top of the Mohs scale, and it is prized for its brilliance and fire. It exists colorless, but also in many colors.

To describe a diamond, gemological laboratories use four criteria, the “4Cs,” defined by the Gemological Institute of America (GIA): carat, clarity, color and cut.

Weight, measured in carats

One carat equals 0.2 gram. The price of a diamond rises faster than its weight: at equal quality, a one-carat stone costs significantly more than two half-carat stones. Setting a budget therefore helps you decide which weight to aim for.

Weight does not tell you everything about apparent size. As a guide, a round half-carat diamond measures approximately 5.2 mm across, and a one-carat diamond approximately 6.5 mm. The piece matters too: the center stone of a ring is usually larger than the stones in a pair of earrings.

Clarity

Clarity measures the presence of inclusions, observed under a 10x loupe. The GIA scale has eleven grades, from FL (flawless) to I3. The last three grades (I1, I2, I3) correspond to inclusions that are often visible and can dull the stone.

In practice, above half a carat, a clarity between VVS and SI1 generally gives a stone whose inclusions cannot be seen with the naked eye. For a diamond worn every day, VS or SI clarity is perfectly suitable.

Color

Color is graded on a scale from D (colorless) to Z (light yellow tint). From D to F, a diamond is colorless; the difference between D and E is barely perceptible, while the price gap can be significant.

On white gold or platinum, people often choose between D and H, for a crisp white. On yellow gold, an I or J color can work well: the tone of the metal softens the perception of a slight tint. For example, a G to I color paired with VS or SI clarity offers a good balance.

Cut

Cut is probably the criterion that matters most for sparkle: a very pure, very white diamond loses its life if it is poorly cut. Laboratories grade the quality of the cut, polish and symmetry; aim for at least “Very Good,” the top grade being “Excellent.”

Shape is a matter of taste: round, pear, oval, cushion, emerald, marquise… The round brilliant remains the benchmark for sparkle; so-called fancy shapes are often slightly less expensive at equal weight.

Natural or lab-grown?

A lab-grown diamond is made in a laboratory. It has the same composition and the same hardness as a natural diamond, which is mined. For the surrounds of the Gentiane ring, we offer both, as you prefer.

The report and the love at first sight

For an important stone, ask for a report from a recognized gemological laboratory: it describes each of the 4Cs and identifies the stone. And do not forget what matters most: a diamond is chosen for the pleasure of wearing it, not as an investment.

Would you rather talk it over in person? We welcome you by appointment at our workshop, 44 rue de Rouen in Saumur, France, or you can write to us from our contact page.