A diamond grading chart is a rating system for the internal characteristics and surface conditions of diamonds developed by the GIA, an independent non-profit laboratory that rates and certifies diamonds. The chart consists of four categories by which each diamond is rated: clarity, cut, color and carat.
The four C's of diamond grading are universal, and allow GIA and other appraisal companies to make unbiased assessments of individual stones. Color refers to the diamond's color in a controlled lighting environment, and the ratings run from D to Z, with D being colorless and Z being strongly yellow.
Clarity refers to the diamond's clear or clean appearance and takes into account imperfections that aren't visible to the naked eye. The higher the clarity rating, the more valuable the diamond. Carat is the measurement of a diamond's size. Two diamonds with the same carat weight could be different widths due to their shapes. The cut of a diamond does not refer to the shape, but rather the symmetry and proportion of the stone.
Diamonds must be assessed before they are set in order to get an accurate grade. The diamond's rating affects the value and price of the stone. The rating system helps consumers ensure they are getting a fair price and that the stone meets certain quality standards.