Choosing a diamond is a decision that should be made carefully. Not because of a trend, but because each diamond has a distinct optical behavior and a value that depends on four very specific factors. In this guide, we explain exactly how a diamond is professionally evaluated: the so-called 4 Cs (Carat, Cut, Clarity, and Colour), their order of priority, and how to apply this criterion when buying an engagement ring, a wedding band, or any diamond jewelry.
We have been doing this since 1981. At Cresber, we select each diamond in international markets according to our own gemological criteria and certify its quality before incorporating it into a piece. What follows is the same criterion we apply every day in the workshop.
What are the 4 Cs of a diamond
Professionally, a diamond's quality is evaluated according to four objective characteristics, internationally known as the 4 Cs:
- Cut — how the stone has been cut.
- Colour — the diamond's hue.
- Clarity — internal inclusions.
- Carat — weight, measured in carats.
These four criteria are used by the GIA (Gemological Institute of America), the most widely accepted international standard, and are the ones that appear on any reputable gemological certificate.
The recommended order for evaluating the 4 Cs
One of the most common questions in the atelier is: "what should I look at first?" Although all four characteristics are evaluated together, at Cresber we recommend analyzing them in this order of priority:
- Cut — first, because it determines how the diamond sparkles. A poor cut ruins any stone, no matter how pure or white it is.
- Colour — second, because it influences the visual perception of the diamond in the finished piece of jewelry.
- Clarity — third, because beyond a certain level, the differences are invisible to the naked eye.
- Carat — fourth, because it is the factor that most influences the price, but also the easiest to adjust according to budget.
Buying a heavy diamond with a poor cut is a common mistake. A smaller, well-cut stone is preferable to a large, poorly cut one.
Cut: how the stone is cut
The cut is the only one of the 4 Cs that depends on human work, not nature. That's why it's the most important.
Cutting a diamond (an art called lapidary) involves shaping the rough stone so that light passes through it as efficiently as possible and transforms into sparkle. Highly specialized lapidaries study each rough diamond, calculate the optimal angles, and decide which cut will achieve the maximum optical performance from that particular stone.
An excellent cut makes the diamond reflect and refract light, creating the three visual effects we associate with the brilliance of a good diamond:
- Brilliance — reflected white light.
- Fire — dispersion into rainbow colors.
- Scintillation — flashes of light as the stone or observer moves.
The GIA classifies cut into five grades: Excellent, Very Good, Good, Fair, and Poor. For quality jewelry, we always recommend Very Good and above.
Colour: what hue the diamond has
The color of a natural diamond is measured on a letter scale from D to Z, where D is an exceptional white (completely colorless) and Z is a very noticeable yellow.
| Category | Letters | Description |
|---|---|---|
| Colorless | D, E, F | Exceptional white. Maximum visual purity. |
| Near Colorless | G, H, I, J | Very slight color, practically imperceptible once set. |
| Faint Color | K, L, M | Slight yellowish tint, already visible to the naked eye. |
| Very Light Color | N–R | Noticeable yellow. |
| Light Color | S–Z | Evident yellow. |
The absence of color allows light to pass cleanly through the diamond, breaking down into the colors of the rainbow like a prism. The closer to D, the more valuable the stone.
Practical recommendation: for engagement rings, D-F grades are the most sought-after range, but G-H offer excellent value for money, as the color difference is practically invisible once the diamond is set in the jewelry.
Clarity: what purity the diamond has
Clarity refers to inclusions: the small internal marks that nature left when the diamond crystallized. They are part of each stone's personality and, for the most part, do not affect its beauty or durability.
But with the other three Cs being equal, the fewer inclusions a diamond has, the more cleanly light passes through it, and the more valuable it is.
The GIA clarity scale, which is used on Cresber certificates, is as follows:
| Category | Code | Description |
|---|---|---|
| Perfect Diamond | FL (Flawless) | No internal or external inclusions, even with 10x magnification. Extremely rare. |
| Internally Perfect | IF (Internally Flawless) | No internal inclusions. Only minimal external marks. |
| Very Very Small Inclusions | VVS1, VVS2 | Minimal inclusions, difficult to see even with magnification. |
| Very Small Inclusions | VS1, VS2 | Small inclusions, visible with magnification but not to the naked eye. |
| Small Inclusions | SI1, SI2 | Inclusions visible with magnification, sometimes to the naked eye. |
| Obvious Inclusions | I1, I2, I3 | Inclusions visible to the naked eye. May affect transparency. |
Practical recommendation: for everyday jewelry, VS1-VS2 is the optimal balance between beauty and price. Inclusions of VVS or higher are indistinguishable to the naked eye, and paying the difference is only justified for investment pieces or collector's items.
Carat: how much the diamond weighs
A diamond's weight is measured in carats (abbreviated ct). One carat is equivalent to 0.2 grams and is divided into 100 points. Thus, a 75-point diamond weighs 0.75 ct.
Weight is the factor that most influences price: the heavier the weight, the rarer and more expensive it is. But weight alone does not determine a stone's value. Two diamonds of the same carat can have completely different prices depending on their cut, color, and clarity.
An important idea: the visible size of a set diamond also depends on the cut and how it has been cut in height. A well-cut 0.80 ct stone can appear visually larger than a poorly proportioned 1.00 ct stone.
How to buy a diamond wisely
Professionally, a good diamond is not chosen by just looking at a certificate: it is chosen by balancing the four characteristics and understanding the intended use of the jewelry.
At Cresber, we always follow the same process:
- Define the use of the jewelry: daily engagement ring, anniversary piece, party jewelry. The use determines which characteristics to prioritize.
- Choose the cut first: always Very Good or higher, no exceptions.
- Adjust color and clarity: based on budget, optimizing for the G-H and VS1-VS2 range for maximum economic efficiency without visual loss.
- Decide the weight: the last parameter, once the previous three are clear.
- Verify the gemological certificate: no quality diamond is purchased without a GIA or equivalent certificate.
If you have doubts, the most useful thing is to talk to a gemologist. At the Cresber atelier, we personally attend to each case, show the available diamonds, explain their certificate, and help choose the stone that best fits the project.
Frequently asked questions about choosing a diamond
Which of the 4 Cs is the most important when choosing a diamond?
The cut. It is the only one that depends on human workmanship and determines how the stone sparkles. A very pure and very white diamond with a poor cut loses most of its beauty. That's why we always recommend prioritizing the cut above the other three characteristics.
What clarity is recommended for an engagement ring?
For daily wear, VS1 or VS2 categories are the optimal balance: inclusions are not visible to the naked eye, and the price difference compared to higher clarity (VVS or IF) is not visually justified. If the budget is limited, SI1 is still a valid option if the inclusions are well-placed.
Is a larger diamond of lower quality better than a smaller diamond of higher quality?
It depends on the use. For an everyday piece of jewelry that will be worn for many years, we recommend prioritizing quality over size: a smaller but well-cut and well-proportioned stone looks better over time. For display or investment pieces, size often takes precedence. In any case, a poor cut cannot be compensated by size.
What is the difference between a natural diamond and a lab-grown diamond?
A natural diamond formed in the Earth's crust over billions of years. A lab-grown diamond is cultivated under controlled conditions in a few weeks. Chemically and optically they are identical, but their market value, rarity, and emotional connotation are very different. At Cresber, we work exclusively with certified natural diamonds, unless a specific project requires otherwise.
What is a gemological certificate and why is it important?
It is the document that certifies the four characteristics (cut, color, clarity, weight) and the authenticity of a diamond, issued by an independent gemological laboratory such as GIA, IGI, or HRD. Any diamond of significant value must be accompanied by its certificate. It is the only way to objectively verify what is being purchased.
Can I see the diamonds before making a decision?
Yes. At Cresber's workshop, in the Joyero Park of Cordoba, we display the available diamonds and personally explain their characteristics. The appointment is without obligation. It is also possible to send photos and certificates via WhatsApp for an initial remote assessment.
Do you want us to help you choose the right diamond?
At Cresber, we have been selecting diamonds and designing jewelry in Cordoba for over four decades. If you are thinking of an engagement ring, a custom-made piece of jewelry with a specific diamond, or if you want a gemological appraisal of a stone you already own, you can come to the workshop or write to us directly.
