During field mapping on the WINTINNA and MURLOOCOPPIE 1:250,000 sheet areas, the common occurrence of massive "grey-billy" silcretes containing pebbles of (older) silcrete was noted. More recent work on the DALHOUSIE 1:250,000 sheet has revealed that these silcretes occur throughout central northern South Australia and, in fact, represent the silicified form of a widespread sequence of mature quartz sandstones, in places bearing silcrete pebbles. The authors distinguish this sandstone sequence from the Eyre Formation, with which they consider it has been included in most previous work in the region. The purpose of this report (to later be published as a Quarterly Note of the Geological Survey of South Australia) is to define this unit as the Mount Sarah Sandstone.