June 05, 2025
Greenalite [Fe3Si2O5(OH)4] is an Fe(II)-serpentine mineral that was first identified in Lake Superior iron formations over 100 years ago, but its true extent is only now being recognized with the advent of in-situ nanoscale techniques. In the last decade, nanoparticulate greenalite has emerged as a prime candidate in the deposition of early Precambrian banded iron formations (BIFs). Together with experiments and modeling, new light is being shed on greenalite-forming conditions and environments, challenging long-held models that argue that BIFs were deposited from seawater as biologically oxidized phases of Fe. Greenalite–hisingerite minerals also occur as alteration products in meteorites, and recent in-situ and orbital data imply that Fe-serpentines are major products of serpentinization systems on early Mars, potentially recording widespread H2 production.
Geochemical Society members can access this issue now via the Elements website using your email address (UserID) and member number (Password).