As they passed blocks of burned, abandoned buildings, empty lots, and wrecked or stripped cars, he slipped a gold chain over his head and handed it to her. The pendant attached to it was a smooth, glassy, black rock. Obsidian. His name might be Rock or Peter or Black, but she decided to think of him as Obsidian. Even her sometimes useless memory would retain a name like Obsidian. She handed him her own name symbol—a pin in the shape of a large golden stalk of wheat. She had bought it long before the illness and the silence began. Now she wore it, thinking it was as close as she was likely to come to Rye. People like Obsidian who had not known her before probably thought of her as Wheat. Not that it mattered. She would never hear her name spoken again.
Both Obsidian and Rye found symbol for their names and despite the many possible ways that it might be interpreted they found a way to define themselves.
This passage also gives some insight on what the world of this story looks like. its is very run down or deteriorated and very un liveable. There are parts in the story where rye details the risk of travelling between cities. Where one could be robbed or killed.