Gold was an extremely valuable mineral in Middle-earth, but not nearly as valuable as mithril.
A portion of gold was used in the creation of Tilkal, to construct Angainor. The treasure of Smaug also contained gold.
Gold was present in the deeps of Arda since its creation by Eru. It was no doubt discovered by Aulë, the great smith who was the first to make use of it. Afterwards, it was to be used by all speaking peoples of earth particularly the Dwarves who mastered it and by the Ñoldor.
In Gnomish, one of Tolkien's early conceptions of an Elven language, the (poetical) word for "gold" is Culu.
- ↑ J.R.R. Tolkien, "I-Lam na-Ngoldathon: The Grammar and Lexicon of the Gnomish Tongue", in Parma Eldalamberon XI (edited by Christopher Gilson, Arden R. Smith, and Patrick H. Wynne), p. 27