A rock fragment, eroded from a rock mass, and deposited in a new location. See Evans et al. (2007) Geograf. Annal. 89, 2 on clast microfabrics; Bourke et al. (2007) Lunar & Plan. Sci. Conf. 38 on fluvial clasts; and Clark (1995) Geology 19, 2 on clast pavements.