Martha Wayne's Pearl Necklace

Martha Wayne's Pearl Necklace was a gift from her mother, who was already a distant woman to Martha, but especially so after she married Thomas Wayne against her family's wish, and were important to Martha because her mother gave them to her after she had married Thomas.
When Thomas and Martha were confronted by Joe Chill, he killed them over her refusal to hand over the necklace, resulting in the necklace breaking and the pearls flying and falling down a sewer drain.
Later still, Bruce's son, Damian Wayne, after having a falling out with his father, tracks down and manages to find two of the pearls to show his father his affection.
After their rediscovery, Bruce would have the two pearls fashioned into earrings for Selina Kyle.