Indexing and Weight Retention

To reiterate, all of the stones in this article have a 57 % table, 33.80 degree crown angle, 21.27 degree star angle, 40.80 degree pavilion angle, and 42.02 degree lower half angle. The only difference is the index of the upper halves and the resultant change in angle of the upper halves.

If girdle thickness remains a constant 3.79% at the mains, crown height and crown angle remain the same.

The 6.00 millimeter 1 index stone, with a 3.79% girdle at the mains and a 5.22% girdle at the halves, will weigh 0.8175 carats. This results in a weight gain of 0.45% compared to the 'normally' cut stone.

The 6.00 millimeter 2 index stone, with a 3.79% girdle at both the halves and mains will weigh 0.8137 carats.

The 6.00 millimeter 3 index stone, with a 3.79% girdle at the mains and a 1.85% girdle at the halves will weigh 0.8086 carats. This results in a weight loss of 0.64% compared to the 'normally' cut stone.

Indexing and Millimeter Spread at the Same Weight

Normalizing all three stones to 0.8174 carats ( the heaviest weight at 6.00 mm from the section directly above ), this is the approximate millimeter spread for each stone:

The stone cut with an index of 1 will have a diameter of 6.00 mm.

The 'normally' cut stone with an index of 2 will have a diameter of 6.01 mm.

The stone cut on an index of 3 will have a diameter of 6.02 mm.