No other natural material is so hard, and hardly any gemstone sparkles so vividly: the diamond is the classic among gemstones. Four characteristics – the 4 Cs – describe how beautiful and valuable a diamond is. Here we explain them to you clearly. At our store on Landstraße 91 in Linz, we are happy to show you the differences on a real stone.
Stand: November 2026
The 4 Cs at a glance
The 4 Cs stand for the English terms Cut, Color, Clarity and Carat (weight). The system was developed by the Gemological Institute of America (GIA) and is now the worldwide standard for describing and comparing diamonds. Only all four characteristics together create the picture of a stone.
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Interactive overview of the 4 Cs by GIA – loads after your consent.
Cut – Cut
The cut is the only one of the 4 Cs that is entirely in human hands. Proportions, symmetry and polish determine how much light a diamond reflects. A well-cut stone deflects the incoming light inside itself and sends it back to the viewer as brilliance – the bright radiance –, as fire – the colored flashes of light –, and as sparkle. If a stone is cut too flat or too deep, light is lost through the bottom and it appears duller, even with the best color and clarity.
Many experts therefore consider the cut to be the most important of the 4 Cs. GIA evaluates the cut of round brilliant diamonds in five grades, from "Excellent" to "Poor".
Interactive display of the cut – loads after your consent.
Color – Color
For white diamonds, the rule is: the more colorless, the rarer and more valuable. The color is graded on a scale from D (completely colorless) to Z (distinctly yellowish). The differences between adjacent grades are so subtle that they can usually only be detected in direct comparison under standardized light. In German-speaking countries, traditional designations are also common alongside the letters:
| GIA Color | Traditional Designation | Description |
|---|---|---|
| D – E | River | exquisite white |
| F – G | Top Wesselton | fine white |
| H | Wesselton | white |
| I – J | Top Crystal | slightly tinted white |
| K – L | Crystal | tinted white |
| M – Z | Cape and deeper | tinted to distinctly yellowish |
The setting also plays a role: In yellow or rose gold, a slightly tinted stone often appears whiter than in white gold or platinum.
Interactive display of color – loads after your consent.
Clarity – Clarity
Almost every natural diamond bears tiny characteristics from its formation deep within the earth: inclusions inside and characteristics on the surface. How many there are, how large they are, where they are located and how well they can be seen determines the clarity. It is assessed with a 10x loupe:
| Grade | Meaning |
|---|---|
| FL / IF | loupe-clean: no inclusions visible under 10x magnification |
| VVS1 – VVS2 | very, very small inclusions, very difficult to find even under a loupe |
| VS1 – VS2 | very small inclusions, difficult to detect under a loupe |
| SI1 – SI2 | small inclusions, clearly visible under a loupe, usually not to the naked eye |
| I1 – I3 (Piqué) | distinct inclusions, partly visible to the naked eye |
For everyday beauty, what matters most is what you can see with the naked eye: A stone with very small inclusions usually looks just as clear on the finger as a significantly more expensive, loupe-clean one.
Weight – Carat
The weight of a diamond is given in carats (ct): One carat corresponds to 0.2 grams and is divided into 100 points – a stone with 0.25 ct therefore weighs "25 points". Large diamonds are significantly rarer than small ones, which is why the price does not rise linearly with weight, but in jumps: A one-carat diamond usually costs many times more than two half-carat diamonds of the same quality.
By the way, this has nothing to do with carats in gold – there it describes the gold content (find out more in our guide). For jewelry with several small stones, the total weight is usually given, for example "0.10 ct" for a Memoire ring.
Interactive display of carat weight – loads after your consent.
Diamond or brilliant?
The two terms are often confused. "Diamond" refers to the material, "brilliant" to a specific cut shape: A brilliant is a round diamond with at least 57 facets that reflect particularly much light. Every brilliant is therefore a diamond, but not every diamond is a brilliant. In addition, there are numerous other cuts such as Princess (square), Oval, Pear, Heart or Emerald cut.
On jewelry pieces, you often see short designations such as "H/SI": The letter stands for the color, the letter sequence after it for the clarity. What such designations mean for engagement rings, we explain in the engagement rings.
Certificate
For larger diamonds, there is often a report from an independent laboratory, such as GIA, HRD or IGI. It records the weight, color, clarity, cut and dimensions of the stone, usually with a report number. Small diamonds, such as those set in Memoire or wedding rings, are generally not certified individually – here the jeweler provides the weight and quality.
Frequently asked questions about diamonds
Which diamond quality is right for me?
That depends on what you value most. A very good cut ensures the most beautiful sparkle. For color and clarity, it does not have to be the highest grade: stones in the white color range with inclusions that cannot be seen with the naked eye are a good balance of beauty and price for many. We are happy to show you different qualities side by side so that you can see the difference for yourself.
Can inclusions be seen with the naked eye?
Generally not with clarity grades up to SI – the inclusions are only clearly visible under a loupe. From grade I (Piqué) onwards, inclusions can be visible without aids and, depending on their location, reduce the brilliance.
Why do two diamonds of the same weight cost different amounts?
Because weight is only one of the 4 Cs. Two stones with the same carat weight can differ significantly in cut, color and clarity – and thus in beauty and price. A stone just below a round weight threshold, such as 0.95 instead of 1.00 ct, can also be noticeably cheaper without you seeing the difference.
Can a diamond break?
Diamonds are the hardest natural material and therefore very scratch-resistant, but not unbreakable: A hard blow at an unfavorable spot can cause a stone to chip. Also have the setting checked occasionally so that no stone is lost – gladly at our store.
You can find more about gemstones, gold and wedding rings in our Jewelry & Watches Guide. We show you diamond jewelry in the Memoire & Diamond Rings, Engagement Rings and Wedding Rings – and of course in person on Landstraße 91 in Linz.
Interactive displays: Gemological Institute of America (GIA)