Diamonds - The 4 C's

The method developed by the Gemological Institute of America determines quality based on the 4Cs.

Color (color)

To accurately determine the color of a diamond, the GIA (Gemological Institute of America) has created a precise color scale. The more colorless (i.e., not yellowish or brownish in tint) a diamond is, the rarer and consequently more valuable it is. This scale is arranged alphabetically and starts with the whitest color D, followed by E,F etc. up to the color Z.

Clarity

Also for the clarity of a diamond, the GIA (Gemological Institute of America) has a precise scale, for which clear determinations are based. If the gemologists do not see any inclusions or blemishes, either inside the stone or on the surface, when graduating, even at tenfold magnification under the microscope, this diamond is called Flawless (FL=loupe clean, flawless), and is undoubtedly an absolutely pure and perfect diamond. If such a gemstone is free of inclusions when magnified ten times, but is not absolutely perfect on the surface (this refers primarily to the polish of the diamond - "minor details of polish are not shown"), then it is referred to as Internally Flawless. The next level describes diamonds with clarity VVS1/VVS2 (Very Very Slightly Included). Here, the inclusions are very very difficult for the expert to see at 10x magnification. Depending on where these inclusions are located (on the surface or, for example, on the side or underside), a distinction is made between VVS1 (better purity), or VVS2. The next purity grade is VS1/VS2 (Very Slightly Included). This grade is given to the diamond when the expert can see very small inclusions only at 10x magnification, and this grade is also divided into 2 gradations; depending on where the minimal inclusions are located here as well. In the SI1/SI2 (Slightly Included) rating, the gemologist clearly sees small inclusions at 10x magnification, and also subdivides these depending on where these inclusions are located. Above this purity, the brilliance is affected. This effect can be seen even by the layman when compared to a brilliant with VS or VVS clarity. At the lowest clarity of the GIA scale, I1,I2,I3 (Included), or better known as Piqué, inclusions are visible to the naked eye. Neither a microscope nor a magnifying glass is needed to see these inclusions, and both brilliance and color of a diamond are negatively affected to the human eye.

Carat weight (weight)

The weight of a diamond is called "carat" (abbreviated ct), not to be confused with the fineness of gold which is called "karat". One "carat" is equal to 0.2 grams - experts divide the carat again into 100 so-called "points". Therefore a diamond with a weight of 0.5 ct is also called "50 points" and weighs 0.1 grams. Although the carat is only a unit of weight, it still allows conclusions about the size of a diamond. The "Rapaport Diamond Specifications"specify concrete minimum diameters for each weight, if they are to meet the high requirements of the quality grades A1 and A2. For example, a round brilliant of one carat must have a minimum diameter of 6.4mm to meet these high standards (A1 + A2) - thus ensuring an optimal price-performance ratio for the end user. Since all prices are based on the "Rapaport Diamond Report" it is guaranteed that a round brilliant not only weighs 1 carat, but also shows 1 carat. However, it must be explicitly pointed out that this only applies to the round brilliant - all other cuts such as emerald cut, heartshape, etc. are excluded from this point.

Cut (grinding)

One of the most important criteria for a brilliant is the cut. There have been many different cuts over the centuries, but the round brilliant cut, as we know it, is still one of the most famous and sought-after. The name brilliant comes from the French and means "shining" (brilliant). In 1919, the Belgian mathematician Tolkowski succeeded in using a fixed number of 57 facets (1 facet is a cut surface) to cut a brilliant so optimally that it achieved perfect brilliance - the measure of all things to this day. But the GIA (Gemological Institute of America) evaluates not only the cut, but the overall cut quality, which also includes the polish and the symmetry. Here we also start with the best - Excellent, followed by Very Good, then Good, followed by Fair. At the very end of this scale is Poor. In order to obtain maximum brilliance, perfect fire and the best light output, a diamond must be cut in accordance with certain dimensions and proportions. The diamond cutter must always keep two things in mind here: A perfect end result and as little grinding loss as possible.

Fluorescence - Luminescence in Ultraviolet Light

About 25% to 35% of all diamonds exhibit this property. Again 95% of these show blue fluorescence, the remaining 5% appear yellowish or white. Fluorescence is the phenomenon that occurs under ultraviolet light. If a stone has blue fluorescence, it secretes blue light under ultraviolet light, that is, it "glows" blue. Depending on the color, fluorescence can negatively affect the appearance of a diamond and may make the stone appear milky. For higher colors (D-F-G), no fluorescence is desired as opposed to lower colors. Here, a blue fluorescence may make the diamond appear more attractive to the human eye - the diamond appears "whiter" than it actually is. This is appropriately positively appreciated on the world market, and prices are thus slightly higher than the Rapaport price index that sets the price. The GIA (Gemological Institute of America) also rates and designates this luminous phenomenon on each certificate with the following gradations: None (No Fluorescence), Faint (Minor Fluorescence), Medium (Medium Fluorescence), Strong (Strong Fluorescence) and Very Strong (Very Strong Fluorescence).

Comments (Comments) 

Under the "Additional Grading Information" an additional information could be indicated under certain circumstances, also called "Comments". This additional information contains further details, which also characterize the diamond, but of course also any other diamond, no matter which cut form. There are both negligible comments, as well as relevant, which can negatively affect the value of any diamond - such as so-called "Color Comments ". For example, if it says "High-Pressure-High-Temperature (HPHT for short), this indicates an artificial color enhancement; of course, a clearly value-reducing comment. The same applies to the addition "Clarity grade is based on a patch of color" - this means, in simple terms, that there is a patch of a different color in the diamond, which has a negative influence on the clarity of the stone. In addition, one does not want any "surface graining" or "internal graining" comments. These so-called Grainings are to be seen with the diamond either on the surface (thus Surface) or in the inside (thus Internal) with a 10x enlargement. These "Grainings" are caused by irregularities in the crystalline growth structure of the diamond and affect the transparency.

The gemologist recognizes fine lines inside the diamond which show graining (internal graining) or a similar structure on the surface of the gemstone (surface graining). The optical appearance under the microscope is similar to that of an extremely fine-grained, milky transparent sandpaper. The "Rapaport Specifications" for highest qualities (A1 and A2) do not accept diamonds with these characteristics (No Color Comment - No Graining Comment). From quality grade A3 on, the so-called "Grainings" are allowed, but the "Color Comments" are still not. 

KEY TO SYMBOL

If a diamond is not flawless, but has inclusions or similar, each GIA certificate contains an additional section titled "Key To Symbols". This rubric shows which blemishes or inclusions are in the respective diamond. Here there are characteristics/inclusions that are considered so-called "allowed", i.e. do not negatively affect the value of a diamond, but there are also those that are undesirable.

Allowed, and therefore neutral are the following:

  • Pinpoint - A very small crystalline inclusion that is equivalent to a small dot.

  • Cloud - a small group of PINPOINTS that resemble a cloud

  • Crystal - Is a crystalline mineral inclusion inside the diamond.

  • Feather - Denotes a "feathery", slightly curved interruption in the mineral structure.

  • Needle - is a fine, elongated crystalline inclusion that resembles a small rod

  • Twinning Wisp - A group of PINPOINTS, CLOUDS or CRYSTALS which often appear in finest ramifications.