The present disclosure concerns a process for the recovery of valuable metals from polymetallic nodules. A two-stage process using SO.sub.2 in an acidic aqueous media is disclosed. In a first step, performed in mildly acidic conditions, Mn, Ni, and Co are dissolved; in a second, more acidic step, Cu is dissolved. Under these conditions, the leachate of the first step contains most of the Mn, Ni, and Co, while being nearly Cu-free. The Ni and Co are precipitated as sulfides; the Mn can be recovered as sulfate by crystallization. Cu, which is leached in the second step, is selectively precipitated, also as sulfide.

A method for the selective precipitation and recovery of manganese from a manganese containing solution, such as a geothermal brine is provided, wherein the geothermal brine is contacted with ammonia, an ammine, or ammonium salt at a pH of greater than about 8.0 to selectively precipitate manganese having a purity of at least about 95%. Also provided are methods for the selective recovery of manganese and zinc from a brine solution.