Hi Tim,
Here's a couple I know of:
"This pearl has become my soul. If I give it up, I shall lose my soul. Go thou also with God."
John Steinbeck, The Pearl
"Again, the kingdom of heaven is like a merchant man, seeking goodly pearls; Who, when he had found one pearl of great price, went and sold all he had, and bought it."
The Bible, Matthew chapter 13 v. 45-46