The eye must be quite relaxed.
The light must be equivalent to that one diffused by a clear sky in North to half day under an average latitude: emission spectrum continuous richer in radiation blue.
Neon tubes are not recommanded (bad), because the emission lines in blue excite the fluorescence of certain diamonds. Even a color temerature of 7,000°K (Kelvin) is also note recommanded. The best lamps must have a color temperature of 6,500 Kelvin and meet the CIE standard (International Commission on Illumination).
Daylight rich UV light (sea, mountain) changes the aspect of a diamond.
The stone must be clean (a dirty girdle obscures diamond and changes its aspect).
Be careful with the stones carrying traces of blue pencil, whose pavilion is coated (clean these traces before estimating the color).
The stone must not be seted.
Observe the diamond on a diamond colortest grader, under an incidence of approximately 30° compared to the pavilion, not to be obstructed by fires and the brilliance.
The master color grading diamond is a non-fluorescent diamond, internally clean (« intelligent » VS2 at best), of size equivalent to diamonds to be tested, correctly proportioned.
If I have a master color grading diamond « a » and « b » located like below:
a diamond of color equal or higher than « a » is « F » at least.
a diamond of color equal or higher than « b » is « H » at the maximum.
a diamond of color ranging between « a » and « b » is « G ». The ideal master color grading diamonds is located exactly at the limit of two grades. Example: the stone « X » located at the limit of the grades Exceptional White (E) and Rare White + (F).
|Exceptional White +
|Diamond disappears almost into the diamond colortest grader.|
|Rare white +
|A light tint is perceptible on side.|
|White||H||A tint is perceptible on side, difficult to see front view.|
|Slightly Tinted White||I - J||A tint is visible front view.|
|Tinted White||K - L||Easily visible tint front view.|
|Tinted Color||M - Z||Tint very easily visible front view (speak sometimes about 1st tinted, 2nd tinted, 3rd tinted, 4th tinted according to the intensity of this colour).|
« D » is the best grade (there is no A, B, or C), and « Z » is the worst grade.
A diamond of really tint is a « diamond of particular color »: Fancy Color. The limit between a tinted stone (Z) and a stone of particular color can be evaluated using a master color grading set. Be careful with diamonds of color artificially modified by irradiation and heat treatment (proof brought by the absorption spectra and fluorescence).
Fancy Color Diamonds have 6 degrees of tints for the Yellow and Brown colors:
And 9 degrees of tints for the others colors:
If the diamond color is yellow (there are diamonds in all the colors: blue, red, pink, green, gray, yellow, etc...). For example: it's a Fancy Light Yellow Diamond or a Fancy Intense Yellow Diamond.
There is a very large range of pink, champagne or cognac-colored diamonds, so it can be difficult to know where to start when looking to acquire such a diamond.
In Australia, there is a very large diamond mine called Argyle that produces fantastic pink diamonds (90-95% of the world's Pink Diamond production comes from this mine), but it also produces the full range of champagne and cognac-colored diamonds.
Argyle developed its own color scale in order to more easily market its colored diamonds, and it quite naturally named this color scale the "Argyle Scale" (illustrated in the image on the right). This scale consists of a series comprising one number and one or two letters; for example, a C3 diamond has a medium champagne color, and C7 designates a cognac diamond.
The GIA gemology laboratory does not use this Argyle scale to classify Fancy Color Diamonds, so how do you know what a C4 diamond corresponds to for the GIA? Simply refer to the (approximate) color equivalence table below.
For diamonds with a pink hue, a 1PP diamond on the Argyle scale corresponds to the most expensive diamond; conversely, a PC1 diamond corresponds to the least expensive of these pink diamonds. PC1 corresponds to a light champagne diamond with a secondary pink hue.
|Color Equivalence Table: Champagne and Cognac Diamonds|
|Argyle Scale||GIA Scale|
|C1: Light Champagne||Color: N, O, P or Q|
|C2: Light Champagne||Color: R, S, T, U or V|
|C3: Medium Champagne||Color: W or X|
|C4: Medium Champagne||Color: Y or Z|
|C5: Dark Champagne||Color: Fancy Brown|
|C6: Dark Champagne||Color: Fancy Brown to Fancy Dark Brown|
|C7: Cognac||Color: Fancy Dark Brown|
A diamond whose color was modified artificially, must be mentioned in section « Comments » on the certificate. You will find these terms « Color Enhanced ».
|GIA||Antwerp||E. O.||AGS||CIBJO - IDC||Scandin. Std.|
|Colorless||D||0+||95||0||Exceptional White +||River|
|F||1+||85||2||Rare White +||Top Wesselton|
|K||5||55||6||Tinted White||Top Cape|
Color Grading Scales for diamonds 0.46 carat and above
GIA: Gemmological Institute of America.
E. O.: Extrême-Orient (Far East).
AGS: American Gem Society.
CIBJO: Confédération Internationale de la Bijouterie, Joaillerie, Orfèverie. International Confederation of Jewelry, Silverware, Diamonds, Pearls and Stones.
IDC: International Diamond Council.
Scandin. Std.: Scandinavian Standard.
What influence does a diamond's color have on its price?
The table below compares the prices for brilliant diamonds of the same weight (from 1.00 to 1.49 carat) but different color grades.
Click on the Image to Update the Data.
Fluorescence comes from a reaction between the energy of the light and the atoms of diamond. In the majority of the cases, this fluorescence is of blue color.
The degree of fluorescence is determined by comparing a diamond with a master fluorescence diamonds grading by exposure to the ultraviolet (UV) rays. If the diamond remains dark, it is not fluorescent.
The fluorescence must be noted like a characteristic on the certificate:
None or Nil
Slight or Faint
A (very) strong fluorescence depreciates diamonds D to H.
A medium or (very) strong fluorescence gives an increase in value to diamonds equal or below I.
|Info Diamond||Diamants Infos||Diamants Infos||Diamanten Infos||Diamantes Infos||钻石: 信钻||Partnership Offer||Gemmes Infos|