the pearl

You can consider themes like greed that consumes people or the cultural enslavement of materialism. I think the Pearl quickly becomes a negative quality. It tears Kino away from all that he once held sacred. It's kind of like the ring from Tolkien's Hobbit series. The longer Kino has it, the stronger its hold on him. Kino knows what the ring represents; a better life for his family. Kino, however, witnesses his life and his family fall apart yet he still cannot part with the ring. With his child dead, it takes the strength of his wife Juana to sever the Pearl's power over him.