In 1975 Blue Circle Cement undertook an assessment of the reserves and quality of deposits of Recent limesand, aeolianite limestone and ferruginous clay which form an active dunefield lying adjacent to BHP's Coffin Bay Tramway in the Port Lincoln district, to determine their potential for use in cement manufacture. Geological mapping was followed by surface sampling of selected exposures for silicate assays, which showed that the aeolianite occurring in the western part of the licence area has a CaCO3 content greater than 90%, but also an MgO content that varies unpredictably between 0.5 and 2.5% (whereas the maximum desirable MgO content for cement making is 1.5%). Since the aeolianite would be the principal material extracted if quarrying were to take place, it was realised that a comprehensive development drilling programme would be required to control the production of material with a consistent satisfactory grade. Because it is necessary to provide silica, iron and alumina as additives to the ingredients of cement to achieve a strong bonding product, these are usually obtained from suitable purity clays or shales. The only available such materials in EL 111 are Tertiary pisolitic clays and laterites, but the investigation showed that these deposits are thin, clay-poor and also highly variable in chemical composition, and thus are likely to be unsuitable to use. Eventually a decision was made that the planned quarrying operation would not be feasible, on the basis both of technical considerations and also of emerging local economic and logistical hindrances.