What metaphors are used in The Black Pearl by Scott O'Dell?

The narrative centers on the gorgeous black pearl, the size of an orange, which Ramun discovers in an undersea cave in a hidden lagoon. It is a metaphor for good and bad. As the fabled Pearl of Heaven, it represents good to Ramun, while the Manta Diablo represents evil. When first found, the pearl has a tiny flaw, which Mr. Salazar trims out, making the pearl perfect.