Eight thin sections of drill core, four cut parallel to and four perpendicular to the core, were received from the Engineering Division of the Electricity Trust of South Australia, for petrographic examination. The core is from an existing well, located near one currently being drilled with the intention of dewatering an aquifer responsible for causing seepage into coal workings near Leigh Creek. Study of these thin sections shows that the aquifer consists of a medium grained quartz sandstone with a minor clay matrix. Porosity in the thin sections is impossible to estimate owing to plucking of material that has occurred during preparation of the sections. Separate well tests have shown that both porosity and permeability are relatively high.