In Dobbs’s story, Petra’s “black rock” serves as a symbol of her character arc as she moves from associating it with the person she wants to be to recognizing in it the person she actually is. Throughout the novel, Petra makes reference to her most prized possession, a piece of coal her Papá gifted to her on her birthday two years prior—“the only thing [she] ha[s] left from [him]” (27). Functioning in the same way a teddy bear to a small child, Petra is always careful to ensure that the rock is in her possession, tucked away safely in her bag at all times. When Petra’s family home is burned down by the Federales early in the novel, Petra forgets to pack her rock in the rush to evacuate and get her family to safety. That she rushes back “into the burning hut,” without hesitation indicates that the rock is valuable enough for her to risk her life in order to retrieve it (27). Later, when Abuelita worries about “[Petra’s] watering eyes,” Petra, rock in hand, reassures her that “[she’s] better now” (27).

Petra sees the object as “more than a black rock,” but instead “a baby diamond” (44).