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Purchasing a diamond is an important decision that requires attention, knowledge, and awareness. For this reason, it is essential to understand the characteristics of the gemstone and compare multiple options in order to find the diamond that best meets your expectations.

The four main criteria used to evaluate a diamond are known as the 4Cs:

Carat – weight

Clarity – purity
Color – color
Cut – cut quality

Carat (Weight)

The weight of a diamond is one of the most important evaluation criteria. It is expressed in carats: one carat corresponds to 0.2 grams and is divided into 100 points.
A half-carat diamond therefore weighs 0.50 ct.

As carat weight increases, the size of the diamond also increases. However, this relationship is not directly proportional. For example, a round brilliant diamond weighing 0.50 ct has a diameter of approximately 5 mm, while a 1.00 ct diamond has an average diameter of about 6.35 mm. As a result, a 2.00 ct diamond will not appear twice as large as a 1.00 ct diamond.

Value is not directly proportional either: a 2-carat diamond of equal quality will cost more than twice as much as a 1-carat diamond, due to its greater rarity.

Cut

Cut is often confused with the shape of a diamond. In reality, cut grading evaluates the diamond’s brilliance, fire, and sparkle.
Cut grades range from: Excellent, Very Good, Good, Fair, Poor

This classification takes into account multiple characteristics that cannot be seen or measured with the naked eye.

The difference between an Excellent and a Very Good cut is extremely difficult to notice. For this reason, it is generally recommended to choose one of these two grades. However, a Good cut can still represent an excellent alternative thanks to its favorable quality-to-price ratio.

In addition to size and cut quality, shape also plays an important role in a diamond’s appearance. The round brilliant cutis considered the optimal shape for enhancing a diamond’s optical qualities, but other shapes also have their own appeal and, all else being equal, usually come at a slightly lower cost.

Clarity

Diamonds form at great depths under extreme pressure and heat. As a result, imperfections in the crystal structure may develop, and mineral inclusions can become trapped within the stone.
The size, color, number, and position of these inclusions and imperfections determine a diamond’s clarity grade. Diamonds completely free of imperfections are extremely rare.

Clarity is expressed using a grading scale that ranges from:

Internally Flawless (IF)
Very Very Slightly Included (VVS1 / VVS2)
Very Slightly Included (VS1 / VS2)
Slightly Included (SI1 / SI2)
Included (I1, I2, I3)

An IF diamond is free from inclusions visible at 10× magnification and represents the highest clarity grade.
In VVS and VS grades, inclusions are very small and generally do not significantly reduce the diamond’s brilliance.
In SI grades, inclusions—although not visible to the naked eye—are more noticeable and therefore have a greater impact on the diamond’s overall value.
In the I (P/I) grades, inclusions are visible to the naked eye and noticeably reduce the amount of light passing through the stone. This represents the lowest clarity grade.

Color

Color is another essential criterion in diamond evaluation. Diamonds are graded on a color scale ranging from D (colorless) to Z (pronounced yellow or gray).

Completely colorless diamonds, such as D and E, are rarer and therefore significantly more expensive. The difference between D and E is extremely subtle; D-grade diamonds exhibit slightly higher transparency.

For colorless diamonds, differences between D, E, F, and G are difficult to detect with the naked eye, although price differences can range from 20–40%.
Grade D is generally recommended for investment diamonds or for those seeking absolute colorlessness.

Diamonds in the H color range are often considered the boundary between colorless and near-colorless diamonds and therefore offer an excellent balance of quality and value, as they show no noticeable yellow or brown tint.

Colors I and J generally appear near-colorless when viewed from the top, although in J-grade diamonds a faint yellow or brown hue may be detected when viewed from different angles.

Grades K and L show a light yellow tint and can be acceptable choices when seeking a compromise to achieve larger size within a limited budget.

Fluorescence

Some diamonds emit visible light—usually blue—when exposed to ultraviolet rays, which are abundant in sunlight.
Fluorescence is graded as Very Strong, Strong, Medium, Faint, or None.

For colorless diamonds (D, E, F, G, H, I), it is generally recommended to choose stones with no fluorescence (none or nil) or slight fluorescence, as strong fluorescence can give the diamond a milky appearance.
For diamonds graded J and below, stronger fluorescence can help mask yellow or brown tones and may improve the stone’s overall appearance.

Laser Inscription

Laser inscription is extremely important. Once the diamond is set into jewelry, it allows you to identify your stone using a simple magnifying lens.
The certificate number—preceded by the logo of the grading laboratory—is engraved on the diamond’s outer edge (girdle), and this inscription must be clearly indicated on the gemological certificate.

Certificate

A diamond must always be accompanied by a certificate. This gemological report describes all of the diamond’s main characteristics.
We recommend purchasing diamonds certified by the following laboratories: GIA, IGI, HRD.

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How to choose a Diamond