Mineral and textural analyses reveal that the basal sandy units of the simple cyclothems of the Pennsylvanian Des Moines series of south central Iowa are well sorted, fine grained to silty, quartzose sandstones. Though always well sorted, the samples from channel facies developments are distinctly more coarse than those from sheet facies developments. Mineralogically the sandstones are composed of stable species derived largely from pre-existing sediments but containing some apparently fresh material from granitic and metamorphic terranes. The light minerals are quartz, orthoclase, plagioclase, muscovite, biotite, and chlorite. Abundant heavy minerals are zircon, garnet, tourmaline, and leucoxene; chloritoid, barite, apatite, staurolite, rutile, anatase, magnetite, hematite, and pyrite also occur. Conditions of deposition, possible provenance areas, and variations in mineral occurrence and abundance are discussed.