§ Of the Beginning of Days The Silmarillion

From the beauty and bliss of Valinor the Valar came seldom over the mountains to Middle-earth, but gave to the land beyond the Pelóri their care and their love. And in the midst of the Blessed Realm were the mansions of Aulë, and there he laboured long. For in the making of all things in that land he had the chief part, and he wrought there many beautiful and shapely works both openly and in secret. Of him comes the lore and knowledge of the Earth and of an things that it contains: whether the lore of those that make not, but seek only for the understanding of what is, or the lore of an craftsmen: the weaver, the shaper of wood, and the worker in metals; and the tiller and husbandman also, though these last and all that deal with things that grow and bear fruit must look also to the spouse of Aulë, Yavanna Kementári. Aulë it is who is named the Friend of the Noldor, for of him they learned much in after days, and they are the most skilled of the Elves; and in their own fashion, according to the gifts which Ilúvatar gave to them, they added much to his teaching, delighting to tongues and in scripts, and in the figures of broidery, of drawing, and of carving. The Noldor also it was who first achieved the making of gems; and the fairest of an gems were the Silmarils, and they are lost.