sentences:  Humboldt had a second but smaller boom in 1934 when the mine reopened, but its duration of operation would be longer under the Shattuck-Denn company of Bisbee, Arizona fame.The Iron King became the most productive mine in the Bradshaws, and produced $100 million in gold, silver, lead and zinc before its closure in 1968.The mine tailings are presently being reprocessed into iron-rich Ironite fertilizer.