There and Back Again
Memoirs had always fascinated Frodo. As a lad, he had begged Bilbo daily to retell the tales of his grand adventure with his doughty dwarven companions.
When Balin had paid them a surprise visit, Frodo had attended eagerly as the white-beard told of rebuilding the Lonely Mountain and filling the Dragon's Desolation with sturdy stoneworks.
Balin's deep voice had resonated with pride for the reconstruction of his forefathers' halls. But Frodo had also heard a hint of longing for his people's once-hallowed home, Khazad-dûm.
Now, Gandalf sighed and put down the Book of Mazarbul. "I fear their end was cruel."
"'And what has become of Balin and Ori and Óin?' asked Frodo.
A shadow passed over Glóin's face. 'We do not know,' he answered. 'It is largely on account of Balin that I have come to ask the advice of those that dwell in Rivendell.'"
The Fellowship of the Ring, LoTR Book 2, Ch 1, Many Meetings