This paper argues that Goethe's collections, in particular his mineralogical collections, had both public and private purposes. The public purposes were closely tied to the tradition of mineralogizing exemplified by the Freiberg Mining Academy. Abraham Gottlob Werner provided technologies for standardizing mineralogical terminology and identification, and Goethe hoped that these technologies would allow for a vast network of collectors and observers who would collate their observations and develop a model of the Earth's structure. His own cabinet, in particular his collection of rocks (Gebirgsarten), was to be a representative sample of rock formations in particular locations that could reveal features of the Earth's structure and history. Goethe was also responsible for the scientific collections of Jena University. He argued that if such collections were to be useful for teaching and research, a goal he strongly supported, they could no longer be treated as the private property of professors. He recognized that social relations within the University would have to be reordered if museums were to fulfil their epistemic functions. In this respect Goethe was on the side of the modern museum and opposed to the world of the private collection and all its idiosyncrasies. However, his own collections had very private and personal purposes. Using some of the ideas of Walter Benjamin as a foil, this paper tries to uncover some of the private passions that fuelled Goethe's almost insatiable collecting. Though these passions were peculiar to Goethe, I argue that historians of science should attend more to the passions and their place in the sciences.