  We report a correlated NanoSIMS-transmission electron microscopy study of the
ungrouped carbonaceous chondrite Northwest Africa (NWA) 5958. We identified 10
presolar SiC grains, 2 likely presolar graphite grains, and 20 presolar
silicate and/or oxide grains in NWA 5958. We suggest a slight modification of
the commonly used classification system for presolar oxides and silicates that
better reflects the grains' likely stellar origins. The matrix-normalized
presolar SiC abundance in NWA 5958 is $18_{-10}^{+15}$ ppm (2$\sigma$), similar
to that seen in many classes of unmetamorphosed chondrites. In contrast, the
matrix-normalized abundance of presolar O-rich phases (silicates and oxides) is
$30.9_{-13.1}^{+17.8}$ ppm (2$\sigma$), much lower than seen in interplanetary
dust particles and the least altered CR, CO and ungrouped C chondrites, but
close to that reported for CM chondrites. NanoSIMS mapping also revealed an
unusual $^{13}$C-enriched ($\delta ^{13}$C$\sim$ 100--200 permil) carbonaceous
rim surrounding a 1.4 $\mu$m diameter phyllosilicate grain. TEM analysis of two
presolar grains with a likely origin in asymptotic giant branch stars
identified one as enstatite and one as Al-Mg spinel with minor Cr. The
enstatite grain amorphized rapidly under the electron beam, suggesting partial
hydration. TEM data of NWA 5958 matrix confirm that it has experienced aqueous
alteration and support the suggestion of Jacquet et al. (2016) that this
meteorite has affinities to CM2 chondrites.
