The transition from the late seventeenth to the early eighteenth century represented an interesting time in the development of the Materia Medica, with the traditional ‘Galenical’ approach being progressively replaced by the ‘Chymical’ approach, a necessary precursor to modern pharmacology. Four surviving complete and partial Materia Medica cabinets belonging to Sir Hans Sloane, John Vigani, John Addenbrooke and William Heberden form the focus for a consideration of changing practices in the medicinal use of geological materials over this period. The working and teaching cabinets contain both processed and unprocessed specimens of geological simples. Of these, some were waning in popularity (e.g. nephrite jade, Irish slate, pyrite and garnets, jet and cannel coal), others were hardly ever used (e.g. belemnites, echinoid spines, Goa Stone, hematite and aetites), whilst others still continued to be popular, either in raw or processed form (e.g. amber, cinnabar, selenite and Terra Sigillata). The collections, considered in the context of contemporary literature, provide a unique insight into this dynamic period in the history of pharmacy.