Polished surfaces of a fine-grained aluminum, silicon carbide metal matrix composite (MMC) were imaged using the ion-induced secondary electron emission in a FIB ion microscope. In these images a dispersion of particles with a distinct bright contrast are seen to be mainly located at the matrix aluminum grain/subgrain boundaries, and at the matrix/reinforcement interface. The particles range in size from 20 to 200 nm. FIB-SIMS was used to identify the composition of these particles as magnesium and oxygen-rich, and so, to corroborate SEM/EDS analyses. Analysis of the FIB images of the polished section showed that the areal density of the particles with distinct bright contrast was consistent with a composition of MgAl2O4.