The rounder the pearl, the better. This is what we often say: "the pearl is round and jade is moist". Round pearls are more beautiful and have first-class luster.

1. Take freshwater pearls as an example. The percentage of the difference between the longest diameter and the shortest diameter of pearls is ≤3% as the standard of perfect circle (A 1 below), the diameter difference ratio is ≤8% as the standard of circle (A2), and the diameter difference ratio is ≤ 12% as the standard of approximate circle (A3). In fact, the roundness of pearls does not need to be measured with a ruler most of the time, and it can be seen with the naked eye. The standard of seawater pearls is higher than that of freshwater pearls, such as exact circle ≤ 1% and approximate circle ≤ 10%. Compare more when buying to see which pearl has better roundness.