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.
