§ Of the Return of the Noldor The Silmarillion

Now the people of Caranthir dwelt furthest east beyond the upper waters of Gelion, about Lake Helevorn under Mount Rerir and to the southward; and they climbed the heights of Ered Luin and looked eastward in wonder, for wild and wide it seemed to them were the lands of Middle-earth. And thus it was that Caranthir's people came upon the Dwarves, who after the onslaught of Morgoth and the coming of the Noldor had ceased their traffic into Beleriand. But though either people loved skill and were eager to learn, no great love was there between them; for the Dwarves were secret and quick to resentment, and Caranthir was haughty and scarce concealed his scorn for the unloveliness of the Naugrim, and his people followed their lord. Nevertheless since both peoples feared and hated Morgoth they made alliance, and had of it great profit; for the Naugrim learned many secrets of craft in those days, so that the smiths and masons of Nogrod and Belegost became renowned among their kin, and when the Dwarves began again to journey into Beleriand all the traffic of the dwarf-mines passed first through the hands of Caranthir, and thus great riches came to him.