Indexing and Weight Retention

If girdle thickness remains a constant 3.79% at the upper half junctions, crown height changes with indexing to maintain the same crown angle.

The 6 millimeter round brilliant cut diamond with a 1 index on the upper halves, with a 3.79% girdle at the halves and a 2.36% girdle at the mains will weigh 0.7748 carats. This results in a weight loss of 4.78 % compared to the 'normally' cut stone.

As we have already seen, the 6 millimeter round brilliant cut diamond with normal ( 2 ) indexing on the upper halves, with a 3.79% girdle at both the halves and mains, will weigh 0.8137 carats or 81 points.

The 6 millimeter round brilliant cut diamond with a 3 index on the upper halves, with a 3.79% girdle at the halves and a 5.73% girdle at the mains, will weigh 0.8664 carats. This results in a weight gain of 6.48% compared to the 'normally' cut stone.