Thin sections of selected areas of lunar rocks returned by the Apollo 11 and 12 missions have been studied by high voltage electron petrography (i.e., transmission microscopy). The techniques involved have been described in detail elsewhere.
Three of the principle minerals present in the samples, ilmenite (FeTiO3), plagioclase (CaAl2Si208) and clinopyroxene (Fe,Mg,Ca)SiO3, were examined and compared with terrestrial equivalents.
Dislocations were evident in all three phases in rock 10029. The arrays, in ilmenite and plagioclase (Figure 1) indicate that mild plastic deformation has occurred. Partial recovery is suggested by hexagonal networks in plagioclase and small dislocation loops in ilmenite. In addition, the plagioclase exhibited extensive twinning and fine precipitates were present in both these phases. “Black spot” images characteristic of radiation damage were found in occasional areas of the plagioclase and pyroxene phases.