The mineralogy and petrology of Parsa, an EH4 enstatite chondrite (Bhandari et
al., 1980), was analyzed with an emphasis on the rare mineral roedderite
[(Na,K)2(Mg,Fe)5Si12O30)] using a scanning electron microscope, a JEOL Hyperprobe,
and a Raman spectrometer. The dominant minerals in Parsa include enstatite (Mg2Si2O6),
kamacite (Fe-Ni alloy, more than 90-95 wt% Fe), troilite (FeS), and taenite (Fe-Ni alloy,
more than 20 wt% Ni), indicating formation under highly reducing conditions. Secondary
minerals include albite (NaAlSi3O8), quartz (SiO2), daubreelite (FeCr2S4),
caswellsilverite (NaCrS2), roedderite, and a mystery Ca-Mg-silicate. The minerals are
fragmented, creating a brecciated texture, with only the primary minerals forming
crystals larger than 300 μm. All minerals are surrounded by FeO(OH), a weathering
product of iron-containing minerals. Both kamacite and taenite contain up to 15 wt% Si,
with more partitioned into taenite. Kamacite contains quartz inclusions, whereas taenite
does not. The metallic minerals demonstrate partial melting, indicating that Parsa’s parent
body underwent a heating episode. Roedderite occurs as elongated euhedral crystals,
commonly as inclusions in troilite. All crystals are less than 15 μm across. K and Na
typically occur in a 1:1 atomic ratio with no apparent zoning. Roedderite contained
within troilite typically forms euhedral to subhedral, unbrecciated prisms with aspect
ratios of ~5, whereas roedderite crystals surrounded by brecciated silicates are typically
anhedral. This difference in morphology may reflect differences in the physical properties
of the troilite and other phases.Bachelor of Scienc
