At the start of 2006 GIA began, for the first time ever, issuing cut grades for round colorless diamonds. Evidence suggests this system, that was meant to help, could actually disadvantage many retailers and consumers.

Background

GIA began a computer ray tracing Cut Study in 1989. In 2001 they were ready to validate computer findings with a human observation survey. But there was only a 58% correlation.

Is this where it seems they went wrong?

• Most of the observations were made by industry participants: only 7% were 'consumers'. Trade observers could be biased in favor of smaller diameter steep crown - deep pavilion diamonds with better yields & profits.
• The lighting GIA used in the survey skewed observer preferences toward deeper smaller diameter diamonds (commercially favourable).
• Diamonds were shown in a gray color tray; conventional wisdom suggests the tray should have been black. A set diamond has little or no light entering from under the stone so leakage areas look dark.

It is also possible the GIA's computer ray tracing was not up to the task (as many experts suggest) or the results would have reduced the Labs revenue (as some critics suggest, although Lab profits support GIA's other worthwhile research).