The colour evaluation of most gem-quality diamonds is based on the absence of colour. A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value. GIA's D-Z colour grading system measures the degree of colorlessness by comparing a stone under controlled lighting and precise viewing conditions to master-stones of establishing colour value.
The colour evaluation of most gem-quality diamonds is based on the absence of colour. A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value. GIA's D-Z colour grading system measures the degree of colorlessness by comparing a stone under controlled lighting and precise viewing conditions to master-stones of establishing colour value.