Tolkien calls the three great jewels in his mythology the Silmarils.
The Silmarils were created by Fëanor, the greatest craftsman among the Elves of Valinor. They captured the light of the Two Trees of Valinor, making them exceptionally precious even before their later history turned them into objects of conflict. Their theft by Morgoth begins one of the central tragedies of Tolkien’s First Age.
Fëanor and his sons swore an oath to recover the jewels, leading to rebellion, wars, and terrible decisions among the Elves. The stories of Beren and Lúthien, Túrin, and the fall of kingdoms are connected to the wider struggle surrounding Morgoth and the Silmarils. They are distinct from the One Ring, the palantíri, and the Arkenstone, which belong to different parts of Tolkien’s legendarium.