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