"However, a withered hand does not seem an unreasonable exchange for a seventh of Voldemort’s soul. The ring is no longer a Horcrux"
-- Albus Dumbledore (HBP23)
A large finger ring, clumsily made out of what appeared to be gold, set with a black stone engraved with the Peverell coat of arms According to Marvolo Gaunt, the ring had been in the Gaunt family for centuries (HBP10). One of Voldemort’s Horcruxes, destroyed by Dumbledore.
After Marvolo's death, the ring passed to his son Morfin, but it was stolen by Marvolo's grandson Tom Riddle on the night that Tom Riddle framed Morfin for the murders of the rest of the Riddle family (HBP17). Tom wore the ring openly for some time afterward at Hogwarts, but apparently after he turned it into a Horcrux he ceased wearing it. Dumbledore found the ring magically concealed in the ruins of the Gaunts' house. Dumbledore managed to "destroy" the Horcrux afterward, in the sense that it no longer functioned as a Horcrux (HBP23, DH33). Dumbledore retained possession of the ring and took to wearing it for a time after its destruction, which left the stone cracked down the middle.
The black stone of the ring is the Resurrection Stone, making it the only Horcrux that is also a Hallow.