They were almost holy, the Silmarils, and the Valar decreed that nothing should ever mar their beauty. No evil shall touch them, nor hands unclean. No mortal flesh shall touch these sacred jewels, lest it become withered and burned, as Varda herself did charge. Mandos, dark and forbidding, came forth to proclaim that the fates of Arda were locked within the heart of the jewels; of earth, sea, and wind, the course was set. Hallowed were the Silmarils.
And Feanor's heart was fast bound to the Silmarils, created by his own hands. They were his, and he was theirs. Forever.