A gold rush is a period of intense migration and mining activity spurred by the discovery of gold. The term can also be used metaphorically to refer to a similar burst in activity associated with the finding of another valuable substance.
In 2254, while discussing the recent discovery of vast deposits of highly pure dilithium on the Pharos siteworld, Captain Christopher Pike suggested it could cause a gold rush, Spock suggested it might ignite a war. (EV comic: "The Fires of Pharos")