Pure Pearls Glossary
Millimetre (mm)
Size & LengthAlso called mm, millimeter
The unit every pearl is measured in. One millimetre of difference is clearly visible on the neck.
A pearl's mm figure is its diameter, taken perpendicular to the drill hole.
The steps are smaller than people expect. A 7mm and an 8mm pearl look distinctly different side by side, and the price gap between them is usually larger than the size gap suggests.
Sellers sometimes quote a range such as 7mm to 7.5mm. That is honest, and it reflects the fact that no two grown pearls are identical.