Valdez-Grijalva, Miguel ANagy, LesleisMuxworthy, Adrian RWilliams, WynRoberts, Andrew P.Heslop, David2022-06-092022-06-090956-540Xhttp://hdl.handle.net/1885/267250Greigite is a sensitive environmental indicator and occurs commonly in nature as magnetostatically interacting framboids. Until now only the magnetic response of isolated non-interacting greigite particles have been modelled micromagnetically. We present here hysteresis and first-order reversal curve (FORC) simulations for framboidal greigite (Fe3S4), and compare results to those for isolated particles of a similar size. We demonstrate that these magnetostatic interactions alter significantly the framboid FORC response compared to isolated particles, which makes the magnetic response similar to that of much larger (multidomain) grains. We also demonstrate that framboidal signals plot in different regions of a FORC diagram, which facilitates differentiation between framboidal and isolated grain signals. Given that large greigite crystals are rarely observed in microscopy studies of natural samples, we suggest that identification of multidomain-like FORC signals in samples known to contain abundant greigite could be interpreted as evidence for framboidal greigite.This research was funded by the Instituto Mexicano del Petroleo ´ (M.A. Valdez-Grijalva), National Science Foundation Grant No. EAR1827263 (L. Nagy), NERC grant NE/J020508/1 (A. R. Muxworthy and W. Williams)application/pdfen-AU© 2020 The authorsEnvironmental magnetismMagnetic mineralogy and petrologyRock and mineral magnetis202010.1093/gji/ggaa2412021-02-14