The Seventy Nine mine is in the Dripping Spring Mountains near Hayden, Arizona. The Paleozoic section, consisting of limestones, shales, and quartzite, has been faulted, sheared, and invaded by a granitic dike system.Cretaceous-Tertiary faulting is prominent and of at least three distinct periods. Initial major north-south normal faulting resulted in the formation of essentially east-west shear zones which were invaded by apophyses of the Central Arizona batholith to form the dike system. Postdike recurrence of the normal faulting produced a shearing of the dikes and shattering of favorable horizons in the adjacent Naco lime-stone. Invading ore solutions penetrating upward along the major faults and shear zones deposited their ores within the shattered North dike and favorable beds of impure Naco limestone. Post-ore faulting has displaced some ore bodies.Approximately $4,000,000 has been recovered between 1919 and 1947 in metals, lead being the most important. Early production consisted of lead carbonate ore from bed replacement deposits. Since 1940 the major production has been from lead-zinc sulfide ore occurring as re-placement veins in the North dike.Hypogene mineralization was deposited in a definite but interrupted three-stage sequence. Early pyrite was shattered and invaded by sphalerite, "argentiferous" galena, and chalcopyrite. Later quartz cuts all earlier sulfides. The bed replacement and upper parts of the North dike vein replacement ore bodies have been extensively altered by oxidation and supergene enrichment. The iron, zinc, and copper content was subtracted, with most galena being altered to cerussite.The ore deposits fall within the mesothermal temperature range.

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