The proper facet alignment, correct facet size, and correct facet angle to maximize the face up Brilliance, Fire, and Scintillation of the diamond.

This is the diamonds reaction to ultraviolet light. The most common color fluorescence is blue and is graded by GIA on a scale of None, Faint, Medium, and Strong. In lower color diamonds such as K, L, and M, strong fluorescence will make the stone face up whiter and thereby provides excellent value for your money. Contrary to popular reports, strong fluorescence does not negatively affect a diamonds color or transparency.

This is the flat plane facet at the top of the diamond.

The height of a diamond measured from the top of the stone (table facet) down to the point (culet facet) divided by the width of the diamond. Depth percentage affects a diamond light performance, as shallow and deep stones will leak light out through the side and bottom that results in a face up opaque and glassy look.