Whats size got to do with quality?

As with all gems, the a larger size of a gem usually indicates greater rarity. With depending on the oyster type that produced it. Japanese Akoya pearls tend to be much smaller than South Sea pearls, due to the fact that the Akoya Oyster is physically much smaller its South Sea counterparts which is nearly three times its size.

So how large can pearls get?

Typically, South Sea pearls, are considered to be the largest, ranging from 9-15+mm in diameter. Whereas Japanese Akoya pearls are considered to be more petit, generally ranging from 5-8mm.

So how do you measure a pearl?

Pearls are measured with a tool called a gauge which measures the width of the pearl in millimetres or mm. Typically, pearls are measured in millimeters or half millimeters increments.