Summary: Rosasite and aurichalcite occur with other copper, zinc, and also lead minerals in Masson Cavern, Rutland Cavern, and other workings in the Heights of Abraham, Matloek Bath, Derbyshire. Partial analyses of two specimens each of rosasite and aurichalcite show Cu : Zn ratios typical of the respective species. They appear to have been formed by the action of solutions containing zinc on disseminated chalcopyrite. The infra-red absorption spectra of malachite, rosasite, aurichalcite, and hydrozincite, examined by the mull technique, are shown to fall into two groups corresponding with the structural groups established by X-ray work. Twin absorption maxima at O-H stretching frequencies are present in the spectra of malachite and of rosasite.