The
rarest and most sought after colour in a diamond is
the most colourless one often called 'blue white' or
'Gem' stone.
Laboratories
give different labels and values to colours.
The
GIA will start at the 'D' of the alfabet ending with
'Z'
The
HRD follows the European 'CIBJO' grading system from
'exceptional white+' down to 'tinted colour'.
The
IGI, EGL and DIAMEX follow basically both these guidelines.
