The microstructures of eutectics between compounds were studied for systems MnO-MnS, NaCl-NaF, NaBr-NaF, LiF-NaF, and FeO-FeS. With the exception of FeS, all the compounds had the NaC1-type structure. In the systems having only NaC1-type structures, the lamellas of the two eutectic phases had matching crystal orientations. There was less consistency among the eutectic systems, however, than bet...