A HREM study of nonbasal twinning and superlattices in ilmenite

The microstructures of natural ilmenite found in Panzhihua district, China, were examined by high-resolution electron microscopy (HREM). The [20] structural images showed clearly the (101) nonbasal twinning which seems to be coincident with the [012] rotation twinning. The superlattices with periodicities of 16.8 and 12.6 Å, respectively, as well as the unit-cell twinning related to the ordering of (101) multiple twinnings were observed. The superlattice resulting from the ordering arrangement of (101) stacking faults related to the slip systems suggested by Heuer [Philos, Mag. (1966), 13, 379-893] were also detected. Possible genetic aspects are considered.