• Inspect the drill hole for a dark brown line where nacre begins.
• South Sea pearls are known for their thick nacre.

The one fact that cannot be overstressed in valuing pearls is nacre thickness. This factor alone is what gives a pearl its luster, orient, color, iridescence and even longevity. Yes, pearls wear out. The thicker the nacre, the longer the pearl has had to grow, and the longer its life. Again, natural pearls are all nacre, cultured pearls have a mother of pearl nucleus which the nacre grows around. With rising production costs there is greater tendency to harvest pearls before they’ve had a chance to produce a thick enough nacre to give them the quality they deserve, and you want. Tips on how to judge nacre thickness include:

1. For perspective, natural pearls are 100 % nacre. Top quality South Sea cultured pearls will consist of no more than 50%, and the average nacre thickness is typically between 10 and 15%.

2. Look for orient and deep luster. Good indicators of thick nacre.

3. Look for cracks, peeling and bands of color. These are sure signs of thin nacre.

4. If you are still unsure, and are about to spend a lot of money on a string of pearls, have a lab report done on them. Call the Gemological Institute of America for a qualified lab in your area.

Answer to quiz: c