Iron rush

An iron rush is a period of intense migration and mining activity spurred by the discovery of iron. A major iron rush took place in the late 22nd century in the Ferrous-Asteroid Belt when it was discovered that the asteroids there were composed of almost-pure iron. Many asteroids were stripped or blown up until it was determined that the destruction of the belt was threatening nearby planetary orbits and all further mining was outlawed, ending the rush. (TOS comic: "The Trial of Captain Kirk")