The diamond shape is different from the diamond cut in the sense that the shape is the external geometrical outline while the cut refers to the distinctive quality of a given diamond consisting of its facets, dimensions, proportions and symmetry, that work together to accentuate its reflective qualities and dazzling effects.
The cut of a diamond refers to the assessment of the light performance and reflective ability of the stone based on a combination of the various factors as created by the diamond designer, including dimensions, symmetry and polish (the overall surface condition of the facets of the diamond).
The brilliance and fire produced by a diamond stone is determined by the fineness of the cut. The finer the cut, the higher the brilliance. Two diamond stones of similar shape may differ in brilliance and appeal as a result of the difference in the cut employed in the making of the two stones.
The cut is the most complex of the 4Cs (Cut, Color, Carat, Clarity) to analyze. The quality of a diamond cut can be determined by studying the interaction of the facets with light and how they combine to create the following visual effects:
Brightness: This is the extent to which white light is reflected internally and externally by the diamond.
Fire: The dispersal of white light into all the colors of the rainbow.
Scintillation: The degree of sparkle produced by the diamond, and the light and the dark patterns created as a result of the reflections within the diamond.
The Gemological Institute of America (GIA) graded diamond cuts into five, ranging from Excellent to Poor and this is the standard scale for grading diamond cuts.
Parts of the Diamond Stone
The widest surface area on the top of the diamond is known as the table. The part that slopes outwards from the table/top is the crown. At the edge of the crown is a wide circumference called the girdle beyond which another slope occurs downwards and inwards. This slopy surface area is the pavilion, and it culminates at a central point at the bottom of the stone known as the culet.
The Pavilion Depth
Shallow Cut Diamond
A pavilion depth that is too shallow will allow escape of light from the sides.
Deep Cut Diamond
A pavilion depth that is too deep will allow escape of light through the bottom.
Ideal Cut Diamond
A stone with an excellent cut will direct most of the light through the crown.
This is the way the facets are shaped and angled to form the patterns on the diamond.
Step Cut Faceting
Here, facets are created as long patterns arranged in rows to simulate a staircase.
Brilliant Cut Faceting
This is a pattern created with triangular facets facing outwards from the center of the diamond.
How well the dimensions, surfaces and facets are positioned to interact in the creation of the desired sparkle and brilliance is what sets one piece of diamond apart from the others. These factors combine to give the diamond its appeal, beauty, and to a great extent contribute in determining the price of a particular stone.