Discovery and structural characterization of zolenskyite, FeCr ₂ S ₄ , in the Muonionalusta meteorite: Advancing micron-scale mineralogy in planetary science

Abstract Here we present the first single-crystal X-ray diffraction analysis of zolenskyite, a chromium-bearing sulfide mineral (FeCr 2 S 4 ) and newly identified polymorph of daubréelite, discovered in the Muonionalusta meteorite, a well-characterized IVA iron meteorite. Zolenskyite occurs as rare micron-scale grains associated closely with daubréelite and stishovite, within a troilite matrix. Chemical analysis confirms a pure, homogeneous FeCr 2 S 4 composition. The crystal structure was refined in the monoclinic C 2/ m space group, revealing a framework of face-sharing octahedra, consistent with a cation-deficient NiAs-type structure, distinct from the spinel-type structure of daubréelite. Zolenskyite forms under high-pressure (>7 GPa) and high-temperature (>1000 K) conditions, probably through solid-state transformation from daubréelite during shock events. The serendipitous recognition of zolenskyite emphasizes the value of careful micron-scale mineralogical investigations in revealing transient or metastable phases that record otherwise inaccessible physicochemical conditions. These findings contribute to understanding the thermal and shock history of meteorite parent bodies and the stability of Fe–Cr sulfides in extraterrestrial environments.