What do the black stones represent in the novel, Homegoing?

The story's two black stones can be seen as representing, on one level, the power of family; and, on another level, how that power is defined by connection with the family's place of origin (Africa).

Early in the narrative, the mother of the two sisters who are the matriarchal ancestors of the two family lines that are the focus of the book's two narrative lines gives each sister a black stone, flecked with gold. The first of the two sisters, Effia, passes her stone to her daughter, and from there it is passed down through the succeeding generations, almost all of whom stay in Africa. The second of the two sisters, Esi, buries hers for safekeeping but is never able to retrieve it. She is sent to America, where all of the subsequent generations in her family / narrative line make their home. Her stone is never retrieved.