When Is a Pearl Round?

The GIA Pearl Description System definition of "round" is: Appears round to the unaided eye, with no apparent variations. This doesn’t mean the judgment is made by casually glancing at a pearl. The pearl must appear round after close examination.

In the pearl industry, the generally accepted standard for round pearls is that diameter measurements taken in several directions vary by no more than 2 percent. Graders and buyers often measure several diameters with a measuring device called a pearl gauge and compare them. Others might roll a pearl on a flat surface or rotate it between their fingers in several directions to determine if it’s round. A pearl that passes this test is sometimes described as an “eight-way roller.”

To judge a pearl strand or other type of necklace for the roundness of its pearls, graders and buyers usually hold the necklace at both ends and gently rotate it. That way, they can detect any possible irregularities in the pearl's roundness.

Sylvia Bissonnette, courtesy J. Grahl Design
For decades, Japanese saltwater cultured pearls have been known for their very round shapes.