Systematic mineralogical and chemical study of the younger Taupo volcanic ash showers, collected from the Terraces Quarry, Taupo, has enabled the showers to be grouped into ten eruptive sequences (numbers refer to the stratigraphical position of the deposits, after Baumgart (1954)): 3; 4; 5–8; 9–13; 14–15; 16; 17–18; 19–22; 23–25; 26. The showers are composed of rhyolitic pumice and finer glass fragments; accessory fragments dominantly of rhyolite, with minor dacite, ignimbrite, and andesite; crystals of plagioclase, hypersthene, and magnetite. The proportions of these components provide a useful guide to distinguishing the showers for correlation purposes. Refractive indices of the glasses show wide variations, even in one pumice fragment, and increase markedly with increased weathering. Correlation of natural glasses by this method must, therefore, be done with extreme care.