New Tool Evaluates Perceived Diamond Size

RAPAPORT… When it comes to the size of a diamond, looks can be deceiving, admits Garry Holloway. Two stones with an identical carat weight might not look the same size due to light leaking out of the stone.

“Most diamonds are cut too deeply, and therefore measure small [in millimeter terms] for their carat weight,” explained Holloway, founder of Melbourne-based Holloway Diamonds.

“Deep-cut diamonds lose brilliance and sparkle, especially at the edges, so they look smaller still.” More than half of 1-carat diamonds look smaller than 0.95 carats, he claimed.

To help trade members and consumers navigate this reality, the Australian jeweler developed a digital tool that uses a diamond’s angles and proportions to assess how large it appears to the human eye.

Holloway has applied for a US patent for Looks Like, a service which calculates how big a round diamond appears relative to the actual carat weight. Users can input key data from a grading report, including the carat weight, depth and table percentage, the crown and pavilion angle, the symmetry grade, and the stone’s dimensions in millimeters. That enables the program — which launched earlier this year — to estimate the degree of light leakage. It gives each stone a rating of small, smaller, big, bigger or average.

In future, Holloway hopes to be able to express the Looks Like size in carats, indicating the size that the diamonds appear to be. That’s not available now, because grading reports only give rounded numbers for crown and pavilion angles. More accurate results would require access to a scanned 3-D model of the diamond, Holloway explained in an interview with Rapaport News. That would also enable Looks Like scoring for fancy shapes, for which grading laboratories do not currently provide detailed cut grades, he noted.

The system also saves data from diamonds that another user has already inputted, enabling future users to obtain the Looks Like results just by providing the grading-report number.

Look Like complements the Holloway Cut Adviser, which Holloway developed in 2000 to help traders and consumers assess the cut quality of diamonds.

Image: Garry Holloway. (Garry Holloway)