What is the symbolism of Clemantine's rock collection in the book, The Girl Who Smiled Beads?

Clemantine's rock collection symbolizes the past. Over the years, Clemantine collects rocks from all the places she and Claire staying, planning to one day give them to Pudi. She sees the rocks as representations of her experiences and memories. Giving them to her brother would allow her to translate the inarticulable aspects of her story. When she loses the backpack filled with the collection, Clemantine is forced to let go of these memories, and the memories associated with them.