The GIA (Gemological Institute of America) has developed a precise color-scale to determine the exact color of a diamond. The more colorless a diamond is (so not with a yellowish or brownish tinge), the rarer and as a result more valuable it becomes. This scale is sorted in alphabetical order. D is the whitest, or better most colorless, followed by E, F and so on up to the color Z.
As well regarding the clarity of a diamond, the GIA (Gemological Institute of America) has a precise scale underlying explicit regulations. If a gemologist does not detect (10x magnification under the microscope) any inclusion or blemish, nor inside the diamond or on its surface, such a diamond may be designated as Flawless (FL – loupe clean, impeccable), and is without a doubt an absolutely clean and perfect diamond. In case, that such a gemstone does not show any inclusions (internally) but maybe some slight imperfections on the surface (which mostly refers to the polish and is stated in the certificate "minor details of polish are not shown"), it is designated as an IF (Internally Flawless- loupe clean/inside). The next clarity level, VVS (Very Very Slighlty Included) refers to diamonds, showing under the microscope (10x magnification) inclusions which are even for a gemologist very very difficult to detect. Depending on the location of these inclusions (surface area or maybe at the side or bottom) one differentiates between VVS1 (superior clarity) and VVS2. The following clarity level is VS (Very Slightly Included). A diamond gets this grading if the gemologist detects at 10x magnification very small inclusions, and again, to be precise regarding the location of these inclusions, VS (Very Slightly Included) is divided in VS1 (superior clarity) and VS2, similar to the previously described VVS-clarity. When it comes to the grading SI (Slightly Included), the expert clearly identifies inclusions at 10x magnification, and again this clarity-level is divided in 2 quality gradings. Here again the same rules apply, depending on the location of these inclusions and the gemologist differentiates between SI1 and SI2. From this clarity-level the brilliance is visibly affected in comparison to a VS or VVS graded diamond – even for the human eye. The lowest grading in the GIA-clarity-scale is I (Included , divided in I1,I2 and I3), or better known under the designation Piqué. Here are inclusions clearly visible with the naked eye and both, brilliance and colour of the diamond are negatively affected.
A diamonds weight is measured in Carat, which may not be confused with the designation Karat of gold. One Carat is equivalent to 0.2 grams – experts divide one Carat into 100 points. A "Half-Carater" (0.50ct) weighs according to that 0.1 grams, and is amongst experts specified as a so called "50-pointer“. Although Carat is a unit of weight, perfect cut Round Brilliants allow a certain conclusion regarding their size (diameter) in connection with their Carat Weight. The "Rapaport Diamond Specifications" require for certain Carat-Weights a minimum diameter in millimeters, but this applies explicitely for a "Round Brilliant". Therefore a "Round Brilliant"of 1 Carat needs to have a minimum diameter of 6.4mm, if this gemstone wants to rank among the highest levels A1 and A2. As the "Rapaport Diamond Report" states the price of a diamond per Carat, this additional requirement regarding the diameter has been established to guarantee, that a final customer does not only pay for a Carat, but receives a "Round Brilliant" which corresponds to the highest standards and shows its "Carat Weight" how it should. But again, this guideline does only apply to the "Round Brilliant" and not other shapes such as Emerald-Cut, Heart-Shape etc..
Furthermore a very important criteria with a Round Brilliant is the Cut. During the last centuries there were various types of cutting; however the Round Brilliant as we know him today, ranks among the most famous and popular. The name "Brilliant“ originates from the french word "brillant“ which means bright or shiny. Tolkowski, the Belgian mathematician, created in 1919 the classic Brilliant-Cut with 57 facets, which resulted in a maximum of brilliance – until today the benchmark. But the GIA (Gemological Institute of America) does not only grade the Cut but in addition also the Polish and the Symmetry. As usual the grading scale starts with the best: Excellent, which is followed by Very Good, Good, Fair and finally Poor. To receive a maximum brilliance, perfect lustre and beautiful sparkle a diamond has to be cut in accordance with certain measurements and proportions. The diamond cutter has to respect always two important things : A perfect final result and a minimum of loss whilst cutting.
Around 25% to 35% of all diamonds share this characteristic. 95% of these show a blue Fluorescence, the other 5% appear yellowish or white. Fluorescence is the phenomenon which occurs under ultraviolet light. If a diamond has a blue Fluorescence he emits under the influence of UV-light a blue color – one may say he "glows" blue. Sometimes a Fluorescence can affect the appearance of a diamond in a negative way, and the gemstone can look milky. With the higher colors (D-E-F) a fluorescence is generally undesirable. When it comes to lower colors, a Fluorescence might be welcome, as it appears to the eye, that a color is more white, than it is in reality. If this applies to a diamond, the world market rewards this with a certain markup (prices are slightly above the "Rapaport Diamond Report"). The GIA (Gemological Institute of America) grades the fluorescence on each Certificate as follows (please see the image from right to left) : None , Faint, Medium, Strong and Very Strong.
Under certain circumstances there might be an extra section below the "Additional Grading Information“ called "Comments“. This addition contains as well important characterizations for all Round Brilliants and of course all other diamonds regardeless of their shape. There are Comments which may be ignored but also relevant ones which may affect the value of a diamond negatively – for example so called "Color Comments". "High Pressure High Temperature (HPHT)" for instance indicates an artificial color improvement and of course lowers the value of a diamond dramatically. The same applies for "Clarity is based on a patch of Color", which means, that there is somewhere inside the diamond a field or an area of a different color which affects the Clarity in a negative way. As well the so called "Graining Comments" are not appreciated; those have to be divided as there exist 2 varieties – "Surface Graining" and "Internal Graining".
These "Grainigs" result due to irregularities of the crystalline growth structure and affect the transparency. The gemologist detects under the microscope (10x magnification) inside the diamond thin lines which contain a very fine granulation (Internal Graining) or a similar structure on the surface of a gemstone (Surface Graining). The optical appearance under the microscope is a little bit equivalent to a slight milky, and very fine sandpaper. The "Rapaport Diamond Specifications" for the highest quality levels (A1 + A2) do not allow diamonds with these characteristics (No Color Comment – No Graining Comment). Quality level A3 allows the previously mentioned "Grainings" but still not any "Color Comment".
KEY TO SYMBOL
If a diamond is not "loupe clean" but has inclusions or certain blemishes, each GIA - Certificate contains an additional category, titled "Key To Symbols". This section shows the nature of the flaws and where they are situated in a particular diamond. There are characteristics/inclusions which may be considered as "allowed", and do not affect the value in a negative way, as well as those which are undesirable.
Allowed and therefore neutral are the following :
a very fine and small crystalline inclusion comparable to a small dot
a small group of Pinpoints forming a cloud
is a mineral,crystalline inclusion inside the diamond
describes a « feathery », slightly curved interruption of the mineral structure
is a fine elongated crystalline inclusion similar to a fine rod
a group of PINPOINTS, CLOUDS or CRYSTALS forming small ramifications
Undesirable and in some instances reducing the value, or rather not permitted by the « Rapaport Specifications » are the following inclusions/defects:
a missing piece/opening, created when a part of a FEATHER breaks away or if a surface reaching CRYSTAL breaks out during the cutting or polishing of a diamond
a particle of the rough diamond remaining under the surface of the polished diamond
a white or transparent crystal which extends to the surface of the polished diamond
a damage (external influences), mostly at a diamonds girdle
the diamonds girdle is not polished but slightly satinated and feels a little bit like very fine sandpaper
the diamonds girdle shows smallest FEATHERS ; those extend to the surface of the gemstone; mostly a result of the cutting
a small impact area showing smallest FEATHERS
an artificial procedure to improve the CLARITY of a diamond using a laser
Basically, on each GIA-Certificate, internal flaws are marked in red, green or black characterizes external flaws.
Simply can be said, and this applies to all diamonds : The higher the quality standard, the less compromises are allowed, and also the "Key To Symbols"
deserve highest attention when selecting such a gemstone.
Since 1981 the GIA (Gemological Institute of America) offers against a small additional fee a special service. Upon request of the customer, the girdle of a GIA-certified diamond can be equipped with a "Laser Inscription". This inscription contains the acronym GIA and the report number (GIA-Certificate-Number) of the relevant diamond. Like this a diamond can be identified without any doubt - a security-service for any client. The "Laser Inscription"
does not take any influence on the COLOR, CLARITY or brilliance of a diamond.
Verifying the identity and value of a diamond
The GIA (Gemological Institute of America) is the world’s largest and oldest independent gem laboratory. The center’s experts are renowned for their reliability and have established themselves as an international benchmark. Founded in Los Angeles in 1931, the institute is the diamond world’s commercially independent authority. The methods developed by the Gemological Institute of America are used to determine the quality of stones using the 4Cs of color, clarity, carat and cut.
Some of the most important and unique diamonds include the Centenary, the Pink Star and the Taylor Burton. Although they all look completely different, these diamonds have one thing in common: they all have a GIA certificate. This is the only document to provide accurate information about color, clarity and other important criteria.
A certificate from this institute is the only way to turn a diamond into an assessable gemstone. A diamond must be properly assessed using strict quality criteria before an accurate price can be drawn up.
GIA applies the strictest criteria to the quality assessment of diamonds
Of course, the GIA is not the only institute to issue certificates for diamonds. In certain aspects of quality, however, these institutes are more lenient than the prestigious GIA, which applies only the most stringent criteria for the certification of diamonds.
This is what makes the GIA certificate the most reliable form of proof in the identity and valuation of a diamond. So that you feel more secure with your purchase, every Koenig diamond weighing more than 0.50 carat comes with a GIA certificate.
Source : Gemological Institute of America (GIA)