In a Pensieve memory, it is revealed that Riddle had taken the gold ring, which has a black stone inscribed with a magical symbol, from his uncle Morfin Gaunt, whom he had framed for the murder of his father and grandparents. Riddle wears the ring while still a student at Hogwarts, but eventually hides it in the house where the Gaunt family had lived. It remains hidden under the floorboards, placed in a golden box, and protected by several enchantments, until Dumbledore finds it.
Dumbledore finds Marvolo Gaunt's ring during the summer break between the events of Order of the Phoenix and Half-Blood Prince. Dumbledore destroys the Horcrux with Godric Gryffindor's sword. Dumbledore is seriously injured by the ring's curses after putting the ring on his finger. The injury leaves his right arm permanently disfigured and would have killed him quickly but for the intervention of professor Severus Snape, who can merely postpone its inevitably fatal effects. The damaged ring is kept for a time on a table in the Headmaster's office.
Before his death, Dumbledore hides the ring's black stone inside a Golden Snitch and wills the Snitch to Harry Potter. Dumbledore had learned that the stone is, in fact, the Resurrection Stone, one of the three Deathly Hallows. This was why he had put it on his finger: he had hoped to activate it and apologize to his long-dead family, quite forgetting it was also a Horcrux now, and thus likely to be protected by destructive enchantments. Voldemort remained unaware of the stone's additional magical properties throughout his lifetime.