Lily had never forgiven her father for her mother's murder. She was killed by a Voldemort fanatic, and to this day, she still holds the belief that had her father has been tougher as head of the Ministry of Magic, her mother would have lived. Lily was stubborn and never forgave him for that. Albus was unsure how he would present this to her. It seemed like a final insult, but Albus knew Harry better than that. He had passed this rock to Lily for some reason, but until he knew why it was better to keep it to himself. Loathe he was to have this stone, useless as it appeared, to be carelessly thrown away in spite of Lily. Years later, it would be Albus" turn to be gracious when Lily revealed her knowledge of the philosopher's stone, and Albus would remember the same stone lying on his desk next to the elder wand and invisibility cloak.