Elements: Greenalite

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.

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