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                                 “

L           “                             “                                      “


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).



DIAMOND CLARITIES (clarity or purity grading)


FL         Flawless – Loupclean                No faults, whether inside or outside, are visible with a loupe

IF          Internally Flawless                    No internal faults visible with a loupe (minor finish faults)


VVS1    Very Very Small Inclusion(s)     Minor faults very very difficult  to see with a loupe

VVS2                “                                                                       “


VS1      Very Small Inclusion(s)             Minor faults very difficult  to see with a loupe

VS2                  “                                                                       “


SI1        Small Inclusion(s)                     Minor faults difficult to see with a loupe

SI2                    “                                                                       “

SI3                    “                                                                       “


I/ P1     Small Inclusion(s)                     Minor faults visible without a loup,

by a qualified observer’s naked eye

I/ P2     Bigger/More Inclusions            Faults highly visible, without a loup, with the naked eye

I/ P3                 “                                                                       “

Nota bene :


. ‘Loupe’ = magnifying lense x 10 used by a trained eye, a qualified observer ; the more pure, the higher the

value ;  professional certification requires additional viewing under a specific microscope ;

. Clarity grading according to presence, absence or abundance, of characteristics / inclusions : the type

(+/- a dozen of different types of  internal or external ‘characteristics’ are in nature), size, location,

quantitiy  which all (might) affect the clarity, hence eventually affect the shine – fire – brilliance – sparkling

of the polished stone ( I/P stones when nicely polished could still sparkle vey nicely ..);

.  Faults can be internal & or external, which is linked the finish/polishing of the stone ;

.  I/P : ‘I’ for ‘imperfect’ or ‘P’ for ‘piqué’.




Cut is linked to the shape or make, the polish of a stone, its proportions, the symmetry and finish.


Polishing requires several manufacturing steps : marking of the rough stone, cleaving or sawing of the rough, bruting (roughly shaping the future end-product), faceting in several stages. Flat facets are being polished and organized in order to form a specific geometric shape ; each facet has to show the right proportions, angles and finish, according to specific rules and percentages hereby enabling the light to travel through the stone (reflection) in the best possible way which in the end will make the stone shine as a ‘brilliant’.

A polished (round) diamond generally shows following sections : a table on top, a crown, a girdle, a pavilion and finally a culet.

A round diamond shows 57 facets + a culet, which will eventually be pointed or faceted. Thanks to the exceptional hardness ’10’ of diamonds the sharp edged facets wont fade away on your beloved diamond jewellery, which will enable you to pass these polished stones on to next generations almost untouched, when set, worn and cleaned properly.


The finish grade, determined according to the proportions and the absence or presence of symmetry deviations, ranges from ‘excellent’or ‘ideal’, down to ‘very good’, ‘good’, ‘medium’ or ‘fair’, ‘poor’.


Thanks to endless creativity and enhanced techniques the polishing has grown through the ages from a few irregular facets on a rough stone, to the most magic sparkling of very elaborate geometric diamond creations.


Common diamond shapes are : the ‘round’ brilliant, the ‘oval’ cut, the ‘pear’ shape or drop, the ‘heart’ shape, the ‘emerald’ cut, the ‘baguette’ cut, the ‘princess’ cut, the ‘radiant’ cut, the ‘cushion’ cut etc.  The best polishers often design original fancy shapes, amongst which the most astonishing geometric creations.


Cabochon stones are generally colour gems, which have been round-polished without facets.





+ ad profile of a cut round diamond (different facets)

+ ad common shapes
In addition to the ‘4 C’s’, cut, carat, colour, clarity, .. the ‘C’ of confidence is getting even more important in order (1) to avoid any confusion between natural diamonds and their many simulants, as well as lab-grown stones ; (2) also viewing full disclosure of any 4 C’s – treatment which might affect the quality, hence the value of a stone.