Heart of the Mountain

A shimmering crystal found by Thráin I beneath the Lonely Mountain of Erebor, and worked into a multifaceted round gemstone by the Dwarves of Durin's Folk. Prized as the Heart of the Mountain, it was kept in the Great Hall of Thráin beneath Erebor. When the Kings of Durin's Folk removed to the Grey Mountains, they took the Arkenstone with them, but when Thrór led the Dwarves back to the Lonely Mountain, he returned the stone to the Great Hall.

When Smaug descended on Erebor and sacked it, Thrór escaped, but he was not able to rescue the stone, and it remained part of the Dragon's treasure-hoard for many years. At last, Thrór's grandson Thorin returned out of exile in the west, but his companion Bilbo Baggins secretly took the Heart of the Mountain from the hoard, and passed it to the Men and Elves who had aided in Smaug's downfall. They in turn used it in an attempt to negotiate a fair recompense from Thorin. All disputes were laid aside when Bolg and his Orcs appeared, and the Battle of Five Armies was fought in which Thorin was slain. The Heart of the Mountain was laid on his breast, in his tomb beneath the roots of Erebor where Thráin had found it long centuries before.