What does Thorin promise Bard for the Arkenstone?

Answer 1

It was the fairest of all the treasurers known to the dwarves. It had belonged to his grandfather at one point. By acquiring it, he was reconnecting with his ancestors and would be established as a great leader in the dwarven community.

Answer 2

The innate greed in dwarves drove him to covet the Arkenstone because it was a massive jewel or extreme brilliance. It was also an heirloom of his line.

Answer 3

alot. it is an heirloom of his family, found in the center of the lonely mountain, hence it's other name- the heart of the mountain.

Answer 4

1/14 of the treasure.