A diamond's light performance depends a great deal on its cut. Its cut grade is measured using an optical device. A three-dimensional object is created to measure its angularity, length, width and depth. All this greatly effects how light travels through it and thus determines its brilliance. Polish and symmetry are also important in this regard. The polish describes the smoothness of the different sides and the symmetry the alignment.
D stands for absolutely colorless. This is the highest grade available. It is rare.
E - A few traces of color can be seen. This is also a rare variety.
Clear diamonds are the most expensive and desirable. However, most diamonds have traces of minerals, scratches or other minute undesirable traits. The GIA and AGSL have a system of rules and standards to summarize the number, location, size, and type of inclusions present in a diamond.
Gemological laboratories issue reports after scrutinizing a diamond. This certificate analyses everything- cut, clarity, colour, dimensions etc.
These reports are reffered to differently by different institutes.
People are often under the false impression that since diamonds are hard they don’t need much care. You need to protect the diamond from getting chipped or scratched.
There are about ten diamond shapes used in jewellery- round, princess (square), emerald (rounded square), asscher (similar to an octagon), marquise, oval, radiant, pear, heart and cushion.