Jill Carattini's article Transfigured tells the story of a priceless discovery:

Barbara Krensavage insisted that clams are not a regular part of her diet. Yet one snowy evening in December she found herself craving an old recipe and so brought home four dozen quahogs—a clam particularly abundant along the Eastern shores of the United States, between Cape Cod and New Jersey. Mr. Krensavage was in the midst of shucking the shellfish for dinner when he discovered one that looked like it was dead. It had a different color to it and he thought it was diseased. As he was about to discard it, Mrs. Krensavage took a closer look.

It wasn't dead. In fact, inside the live clam was a rare, possibly priceless, purple pearl. Experts estimate that roughly one in two million quahog clams contains a gem-quality pearl like the one found by the Krensavages. Due to the great rarity of the find, it has been difficult to even place a value on it, though some have estimated the pearl to be worth hundreds of thousands of dollars.

Possible Preaching Angles: (1) Jesus as the cornerstone rejected by the builders; (2) the Kingdom of God is like a man who finds a pearl of great price.