Diamond Carat and Colour



The weight of a diamond is expressed in carats. 

According to the metric system one ‘carat’, a unity of mass for gemstones, weights 1/5th of a gram ; 1 ct = 0,20 gram

Professional scales round up very precise measurement to one hundred of a carat ; two decimals are mentioned and the third decimal is rounded down as long as it is smaller than 9.     

One carat is devided in 100 ‘points’ – for example a 20 pointer is 0.20 ct. 

One ‘grainer’ is ¼ of a carat or 0,25 ct.  

‘Carat’ takes its name from the Greek ‘keration’, small weight, hence ‘carob’ seed, from the carob tree, all small individual seeds weighing +/- precisely 0,20 grs 

(keration, small weight’ meaning also +/- 1/3rd of a small (religious) contribution, hence the Arabic ‘qirat’). 

Do not confuse ‘Carat’ (ct) with ‘Karat’ (kt) , which refers to the purity of gold

‘1 gram of diamond’ is as heavy/big as a 5 ct diamond ! 

(one round 5,00 ct diamond shows a > 1 cm diameter or 11,00 mm precisely) 



DIAMOND COLOURS (colour grading)

D   Jager                Exceptional White Plus        Colourless             I. Exceptional White 

E   River                   Exceptional White                      

F   River                   Rare White Plus               Near Colourless II. White

—- (colourless through crown) 

G  Top Wesselton   Rare White                                  

H   Wesselton          White                                             


I   Top Crystal       Slightly Tinted White Slightly Coloured   III. Tinted White

J   Crystal                                                                      


K   Top Cape          Tinted White                                  


M-Y  Cape       Tinted Colours  Light Coloured to Coloured   IV. Cape/Tinted  


Z  (Z = fancy yellow) Colour Diamond V. Fancy

Nota bene : 

.  Colour grading is carried out by trained graders by comparing an individual stone to specific master    

   stones and under  a particular light ; the less coloured, the higher the value, except for intense colour 

   diamonds which are generally valued x times more than a comparable colourless diamond, especially 

   when showing a high colour saturation ; 

. ‘Blue White’ colour means the finest (blueish) white colour ;  

. ‘Tinted’ & ‘Cape’ colour means generally yellowish (or eventually brownish, greenish etc.),  

   from ‘faint’ to dark ;

. ‘Fancy’ colour means coloured, from regular to very intense or ‘vivid’ ; a specific colour grading applies on 

   colour diamonds  depending on the intensity of the colour and colour saturation & ‘hue’ (spreading of 

   colour throughout the stone).

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