White Gems of Lasgalen

The White Gems of Lasgalen were fashioned by the Dwarves of Erebor for the Elven queen of Mirkwood. However, the queen fell in Gundabad and never got to wear them. Her husband, Thranduil, came to Erebor to retrieve them, but due to a dispute over payment, was denied them, leading to a severing of his alliance with the Dwarves of Erebor.
Thranduil later tried to offer Thorin freedom and assistance in exchange for Thorin to bring him back the gems, but the Dwarf, still aggrevated at the Elvenking's refusal to help against the dragon, refused. Once he learnt that the dragon Smaug was slain, Thranduil marched upon the mountain to retrieve the gems. However, he soon realized that his relationship with his son (damaged because of his own obsession with retrieving the stones) was of greater significance.