This invention describes a process for producing a nanoscale zero-valent metal, including reduction of a metal ion solution with a dithionite compound, wherein the reduction is carried out under alkaline conditions under substantially an inert atmosphere. A nanoscale zero-valent metal obtainable by this process, and having a new crystalline form, is also described. The nanoscale zero-valent metal produced by the process of the invention is preferably iron, and is advantageously used for the remediation of contaminated water.