Balin and his wife Kera lived in the mountain range, north of the Empire. When they were younger, Kera used to joke about Balin's true love being the mountain, but with the decades, the joke had lost in humor and Kera had gained in bitterness. "This is an absurd place to live, far from other Dwarfs, far from the more populated outposts, far from the richer veins..." Her complains hurt Balin for he loved his wife dearly, although, certainly, nothing could compare to the magnificence of the Mountain. It was just another mountain on the range for everyone else, but for Balin, it always was the Mountain, with capital M.
One night, Balin came back and found the fire out, the pot empty, and their home, cold. Thinking that something must had happen to Kera, he took a lantern to keep the mountain winds from putting out the light, and went out searching for her. He shout her name to the dark until he could not talk anymore, and he finally came back to the house, determined to search again the next day, with sunlight.
Balin lit the fire and, when he got warm, looked around, for any clues about where could Kera had gone. And he found a clue in the shape of a message written with coal over a piece of leather. Dwarves' runes are made to be engraved in stone, a laborious work, so their sentences tend to be as short and clear as they can. Translated, Kera's message would have been more or less "I went back to my family. Be with your mountain."
Sadness and realization overcame Balin while he drop to sit on the floor. He didn't remember having ever felt so alone.
The next day he almost woke up already in the mine, in the last shaft he had opened on the Mountain. He was already hitting the rock with his pick, although he didn't even remember how he got there. He wonder what he was doing, what was the point of discovering the Mountain's secrets and gifts with no one to share them with. And got angry. And then he got furious and started hitting the rock harder, complaining first and then shouting the Mountain for his love for it made him lose his wife.
And then the rock gave way and left a hollow under the pick. At first, Balin didn't understood, lost as he were in his fury, but years of mining took control and he realized he had found a geode, the first one he had found in the Mountain.
And he could hear a child's cry from it.
Astonished, he looked inside the geode, pouring light with his lantern, and saw a little wounded baby inside the geode, crying. Balin knew not what to do but to take the baby out of there, so he took the smaller pick he used when he had to get gems out of the rock, and started hitting as delicately and fast as he could until he could put his hands in and take the baby out. He (he was a "he") was still crying, but Balin's was relieved when he could see better the wounds and realized it was barely more than scratches. He wrapped the baby in his own coat and ran with him back to the house, looking for something else to protect him from the cold and then go down to the hamlet and look for advice about taking care of babies.
For the next months he fed the baby with goat's milk, following the advice of Mara, an old, half-blind dwarf-woman who was also considered half-crazy. At least she was crazy enough to accept Balin's story without questions and giving him the advice the baby needed. For the next years the hamlet's opinion was that Balin had a lover, the mother of that child, and that that was what made Kera leave. Since Mara helped Balin but was too old to be his lover herself, they thought she knew the affair and had helped keeping it secret.
Be as it may, Balin named the child "Berg" and raise him as miner. However, Balin often caught Berg with the sight lost to the horizon and got thinking that a dwarf born from the Mountain wasn't meant to be kept there, less so considering the relationship with the hamlet's people. They kept to the lover's story and so the dwarves Berg's age taunted him, until the day he lost his temper and badly beat a few of them. Finally, Balin decided he should do something for Berg's future but he had grown old by then, and that winter was going to be his last. "I'm dying, son." he told Berg "as grand Mara did. You will be by yourself now, but I think fate has more for you than mining the Mountain. Open that chest" Berg did so and found a piece of a geode, half carved. "I intended to make a shield for you with that, part of the geode you were born from, but I had not enough time or skill. I ask you, take it when you go and find somebody able to make a shield from it, for I hope it'd be a link with your mother's strength in your traveling."