  Djerfisherite is an important carrier of potassium in highly reduced
enstatite chondrites, where it occurs in sub-round metal-sulfide nodules. These
nodules were once free-floating objects in the protoplanetary nebula. Here, we
analyze existing and new data to derive an equation of state (EOS) for
djerfisherites of K_{6}(Cu,Fe,Ni)^{B} (Fe,Ni,Cu)^{C}_{24} S_{26}Cl structural
formula. We use this EOS to calculate the thermal stability of djerfisherite
coexisting in equilibrium with a cooling vapor of solar composition enriched in
a dust analogous to anhydrous, chondritic interplanetary dust (C-IDP). We find
that condensed mineral assemblages closely match those found in enstatite
chondrites, with djerfisherite condensing above 1000 K in C-IDP dust enriched
systems. Results may have implications for the volatile budgets of terrestrial
planets, and the incorporation of K into early-formed, highly reduced,
planetary cores. Previous work links enstatite chondrites to the planet
Mercury, where the surface has a terrestrial K/Th ratio, high S/Si ratio, and
very low FeO content. Mercury's accretion history may yield insights into
Earth's.
