Shell and bone implements survive well in coastal shell middens in the Sydney region but usually only in layers dating to the last 3000 years. Organic materials such as shell and bone, do not often survive longer than 3000 years because of the acidic nature of the Sydney soils. Wood rarely survives even in younger contexts.

Stone implements survive much longer than bone, shell and wood, and are found in open locations as well as rock shelters. Nevertheless, the stone tools provide clues as to how plant and animal materials were processed and help us understand early subsistence methods. (V.Attenbrow)