"The following factors can modify the heavy mineral composition and limit the interpretation of the assemblage in terms of source area conditions: (1) weathering, (2) abrasion, (3) selective sorting, and (4) post-depositional solution. This paper attempts to show that (3) and (4) are of minor importance. In basins with a low rate of sediment supply and under conditions of intense weathering and reworking the others can strongly modify the composition of the heavy mineral assemblage. In basins of rapid deposition deriving their sediment in general from source areas with active erosion, the influence of all factors is negligible and the heavy mineral assemblage directly reflects the petrography of the source area. An example illustrates the type of problem for which heavy mineral analysis is of value."