Chert, silcrete, silicified sandstone and other hard siliceous rocks

Archaeologists have identified chert artefacts at sites along the Murray River in the Loxton-Renmark area of South Australia.  The question of using the correct rock name arises because geological formations in that area are not described with chert as a rock type.  Recently I visited sites of commercial quarries where silicified and ferruginised sandstone is quarried.  Those sites are in Loxton Sands, a formation containing sands and not chert.  For Aboriginal people to have obtained 'chert' for use as stone tools the hard siliceous rocks must have been exposed at the surface, in eroding creeks or along cliff faces.  This is now a new research project; finding sources of hard siliceous rocks and correctly naming the rock types.