Cultured Pearl Size: Basics

When it comes to quality pearls, like most things, size does matter. A key factor in a pearl's value is its size, with the larger pearls generally being the more prized. What size pearl is the best? It depends on many variables. Here is all the information you need to know to make an informed decision

The diameter of every pearl is measured in millimeters, varying from 2 to 20mm and rounded off to the nearest 0.5 mm. Pearls in strands are measured differently. Measurements are taken perpendicular to the drill holes and expressed in half-millimeter ranges, for example, 6 to 6.5 millimeters. A Strand labeled as a 7.5mm strand will be comprised of 7.0mm - 7.5mm pearls, with the smaller pearls being placed near the clasp. If the differential in the strand is greater then 0.5mm then the strand is considered graduated.

• The size and vitality of the mollusk that produced it
• The size of the nucleus. The nucleus is the irritant, such as a bead in cultured pearls, at the heart of the pearl.
• The time that the mollusk spent underwater before the pearl was harvested.

Cultured pearl types, which include the freshwater, South Sea, Akoya and Tahitian, usually have a specific size range. However, culturing practices are changing, and you will find more pearl sizes among the different types.

Traditionally, Akoya(2.0mm - 11.0mm) and Freshwater pearls(2.0mm - 15.0mm) are smaller pearls and Tahitian or South Sea pearls are much larger(9.0mm - 20.0mm). The value of the size really depends on how unusual it is. Large Akoya cultured pearls are not large by Tahitian standards but a large one would be of higher value that a Tahitian pearl of the same size.



Tahitan and South Sea pearls lack tradition when it comes to size. Being relatively recent additions to the pearl market the general consensus is that bigger is better. On the other hand Akoya pearls and to some extent freshwater pearls are steeped in tradition, with very clear guidelines on what size of pearl is best suited for whom.