Nanoparticulate mackinawite was synthesized from elemental iron and sulfur in a convenient and reliable reaction. The structure and composition of the products were characterized and a new model describing the particle characteristics is established.

In this work, three different tochilinite‐like materials have been obtained by sophisticated synthetic methods that allow to control the distribution of iron ions. The purity of the samples was confirmed by powder X‐ray diffraction. From elemental analysis and Mössbauer spectroscopy data, detailed compositions could be determined: T1) Fe0.76S*0.86 [Fe2+0.01Fe3+0.56Mg2+0.43(OH)2.01]; T2) Fe0.89S*0.85 [Fe2+0.55Fe3+0.11Al3+0.33(OH)1.84(O)0.16]; T3) Fe0.71S*0.79 [Fe2+0.25Fe3+0.73Mg2+0.01Al3+0.01(OH)1.98(O)0.02]. These compositions fit to typical compositions of tochilinite in regard of the amount of iron vacancies and the volume ratio of the hydroxide layers to the sulfide layers. Besides hydroxide ions, oxide ions are also present in the hydroxide layers as a result of surface oxidation after the synthesis due to the high reactivity of the particles. TEM and SEM investigations show that the obtained powders consist mainly of thin sheets accompanied by nanotubes with BET surface areas ranging between 20 m2/g and 40 m2/g. The thermal stability was investigated by TGA and DSC analysis and it depends significantly on the composition.

The cover picture shows that pure tochilinite‐like samples can be prepared from nanoparticulate FeS with mackinawite structure under mild hydrothermal conditions. The samples have been characterized by various methods including Mössbauer spectroscopy. TEM and SEM revealed the tochilinite analogues to consist mainly of thin sheets accompanied by nanotubes. The following compositions could be determined: Fe0.76S*0.86[Fe2+0.01Fe3+0.56Mg2+0.43(OH)2.01], Fe0.89S*0.85[Fe2+0.55Fe3+0.11Al3+0.33(OH)1.84(O)0.16], and Fe0.71S*0.79[Fe2+0.25Fe3+0.73Mg2+0.01Al3+0.01(OH)1.98(O)0.02]. More details are discussed in the article by R. Bolney, M. Grosch, M. Winkler, J. van Slageren, W. Weigand, and C. Robl (DOI: 10.1002/zaac.202200219).

Mackinawite has unique structural properties and reactivities when compared to other iron sulfides. Herein we provide evidence for the mackinawite‐supported reduction of KCN into various reduced compounds under primordial conditions. We proposed a reaction mechanism based on the nucleophilic attack by the deprotonated mackinawite ‐SH surface groups at the carbon atom of HCN. The initial binding of the substrate and the subsequent reduction events are supported by DFT calculations and further experiments using other substrates, such as KSCN, KOCN and CS2. Until now, conversion of CN− into CH4 and NH3 has been limited to nitrogenase cofactors or molecular Fe‐CN complexes. Our study provides evidence for mackinawite‐supported cleavage of the C−N bond under ambient conditions, which opens new avenues for investigation of other substrates for mackinawite‐supported reactions while shedding light on the relevance of this type of reaction to the origin of life on Earth.

The cover image was inspired by multiple artistic presentations of the Archean habitat shortly after the formation of the Earth. It is assumed that the early Earth featured a generally craggy environment that frequently suffered impacts during the early and late heavy bombardment. The atmosphere mainly contained water vapor and CO 2 and was much denser than the present one. The final image was produced by using the opensource 3D computer graphics software, Blender.