• Natural pearls are sold by carat.
• Round pearls, the most valuable shape, are measured in diameter.
• Location of origin makes a huge difference in what size you should expect.

Cultured pearls are sold by size, not weight like other gems or even natural pearls. Size, in pearls terms is considered in millimeters. Round pearls are measured in diameter, and symmetrical and baroque gems are measured in width and length. Natural pearls, on the other hand are sold by the carat, just like diamonds. Just to help put size into perspective:

1. South Sea pearls are much larger than Japanese Akoya pearls.

2. In Japan, a 7 millimeter pearl is huge but in the South Sea’s the same size is tiny.

3. Price jumps dramatically in Japanese pearls over 8 millimeters.

4. The price jump for South Sea pearls is at 15 mm.

Now, you may wonder why they don’t just plant a really big mother-of-pearl nucleus in the mollusk to make bigger pearls. If only it were that simple. The bigger the nucleus, the more likely the mollusk will reject it, and may even die in the process. Also, the larger the nucleus, the less nacre, the less nacre, the less luster and value.

Answer to quiz: c