Arkosic quartzites of Pre Cambrian age contained in the Torrensian, Sturtian and Marinoan series occur in the Adelaide Hills. The largest deposits are in the Torrension series, in which several alternative quarry sites have been located. Adequate quantities of stone are available at these at alternatives to maintain quarrying operations for some years. Most of the areas mapped as Stonyfell Quartzites, however, are poor quality stone, unsuitable for use in civil engineering projects.