The 4Cs of Diamonds (How to classify Diamonds)

GIA (Instituto Gemologico da América), which is an American non-profit institution and a world authority on diamonds, colored stones and pearls, created the “4Cs” and the International Diamond Classification System ™ in the 1940s – until today , the world standard for assessing diamond quality.

In general, the 4Cs correspond to: color, clarity, cut and carat weight. Through this universal method it is possible to establish the quality of any diamond, anywhere in the world.

  1. Color 
  2. Clarity
  3. Cut
  4. Carat Weight


Diamonds can be completely colorless, or they can have shades of yellow and brown. The most valued are the colorless ones, that is, the less color, the greater its value.

Out of this concept are diamonds of extravagant colors, such as roses and blues, for example.

As we have seen, GIA has defined a color classification scale for diamonds. This scale is recognized worldwide and used as an industry standard.

The scale starts with the letter D which represents the totally colorless. It continues until the letter Z, containing shades of light yellow or brown.

Each letter grade has a clearly defined range of color appearance. Many of these color distinctions are so subtle that they are invisible to the untrained eye. But these small differences make a big difference in the quality and price of the diamond.


The degree of clarity is based on any natural inclusion (dark spots) found within a diamond.

Diamonds have unique marks that can be internal, called inclusions or external, known as spots. This is because diamonds are formed with extreme pressure and heat.

The clarity of a diamond refers to the absence of these inclusions and stains, it can also be called purity. Diamonds without these marks are very rare and rarity affects their value.

Every diamond is unique and special, None is absolutely perfect with 10x magnification, although some approach this perfection and are known as “Flawless”, the same being extremely rare.

As with color, in the GIA ™ International Diamond Grading System, diamonds are given a degree of clarity ranging from flawless (FL) to diamonds with obvious inclusions.

The GIA Clarity Scale contains 11 degrees, with most diamonds falling in the VS (very slightly included) or SI (slightly included) categories.

When determining a degree of clarity, the GIA system considers the size, nature, position, color, or relief and, in addition, the number of light characteristics visible under a 10x magnification.

3. CUT

The quality cut allows a diamond to express its natural brilliance and flicker.

Cut refers to the quality of a diamond’s proportions and symmetry. These angles allow the diamond to capture light and reflect it, producing brilliance. If a diamond pavilion is very deep, the center will be noticeably darker.

Diamonds are famous for their ability to transmit intense light and brilliance. And the degree of cut of a diamond is analyzed on how well its facets interact with light

Stoning is an art. Precise cutting and finishing are necessary to shape a stone so that its proportions, symmetry and polishing provide the magnificent light return possible only in a diamond.

The cut of a diamond is crucial to the beauty and final value of the stone. And of all 4Cs, the cut is the most complex and technically difficult to be analyzed.

As the round cut is the most used in jewelry, GIA uses this as a standard. She uses facets to determine proportions and assess the face-up appearance and how much the diamond interacts with the light. This interaction generates visual effects such as:

Brightness: internal and external white light reflected from a diamond.

Fire: the dispersion of white light in all colors of the rainbow.

Flicker: the amount of spark a diamond produces and the pattern of light and dark areas caused by reflections within the diamond.

GIA’s degree of diamond cut also takes into account the design and finish of the diamond, including its weight in relation to the diameter, its thickness (which affects its durability), the symmetry of the facet arrangement and the quality of the polishing on these facets.


Diamonds are measured or weighed in “carats”, the equivalent of 200 milligrams. The precision in weighing a diamond is such that a diamond is weighed to one thousandth (.001) of a carat and then rounded to the nearest hundredth.

We normally use weight to buy many types of products, so the general perception is that a larger diamond is more valuable than a smaller one.

However, a 2.00 carat diamond is not always worth twice as much as a 1.00 carat diamond, as the larger ones are rarer and much more valuable. But the value of a diamond is determined by considering all 4Cs of diamond quality

An uncut rough diamond is usually much heavier than a cut diamond. For example, a diamond generally loses 50% -60% of its weight before reaching its final, polished version. The same stone of the same quality will be more expensive if it weighs more carats. It is also important to note that diamond prices increase with a domino effect as they are heavier in carats, as they become more and more disproportionately difficult to find.

It is for the reason described above that diamonds are examined by a number of professionals before the owner (who is also an expert in the field) finally decides what is the best option in terms of what shape it will have, since other factors related to the their quality need to be considered.

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